110222 technical manual passivhaus

The Science of NatureThe Future of Construction

Timber Frame Systems

PASSIVHAUSSolutions with NBT DIFFUTHERM,

NBT PAVACLAD and NBT PAVAROOF

CERTIFICATE No 07/4448

PASSIVHAUS – Background

IntroductionThe definition of a PASSIVHAUS is “a building in which thermal comfort is guaranteed solely by re-heating (or re-cooling) the fresh air that is required for satisfactory air quality”.

The principle of the PASSIVHAUS is a building with no heating system except for the heat recovery through the ventilation unit. If built correctly the buildings are robust, healthy and cost effective. To achieve a PASSIVHAUS strict design guidelines must be followed in relation to:

• Compact design• High levels of insulation• Minimal thermal bridging• Highly insulating window • Very high standards of airtightness• High quality mechanical ventilation with heat recovery

(MVHR)

These are explained in this manual.

HistoryThe PASSIVHAUS concept was first developed by Profes-sors Bo Adamson and Wolfgang Feist in 1988. The first PASSIVHAUS buildings were built in Darmstadt in 1990 and the PASSIVHAUS Institute was founded in 1996. Since that time around 15,000 PASSIVHAUS buildings have been built worldwide, most of them in Germany and Austria. There are now a number of other PASSIVHAUS Standards such as Minergie-P in Switzerland.

Content Background 2 NBT PASSIVHAUS 3 Comparison 4 Airtightness 6 Insulation & Thermal Bridging 7 Roof - Detail & Information 8 Wall & Ceiling - Details & Information 9 Floor - Detail & Information 10 Window - Detail & Information 11 Ventilation Systems 12 Key Considerations - Designers 13 Physical Properties 14

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w PASSIVHAUS is a widely and extensively tested technology which is seen by many as the future of building and the main aim of sustainable construction.

For more information please visit www.natural-building.co.uk

NBT PASSIVHAUS A NBT PASSIVHAUS achieves the PASSIVHAUS standard with the following additional benefits:

• Full technical design and site support from NBT• Full component advice and supply if required• Healthy, non-polluting, ecological materials• Huge amounts of carbon sequestration in the mate-

rials

As buildings become more energy efficient, the embodied energy and embodied carbon become relatively more si-gnificant. NBT PASSIVHAUS (say 100 m2 footprint) with NBT PAVATEX products will lock up over 10 tonnes of CO2 eq. in the woodfibre boards alone, and over 30 tonnes of CO2 eq. including the timber structure. In contrast synthe-tic insulations will emit between 1.3 and 2.5 kg of CO2 eq. for every kg of product used and a standard masonry building will emit over 40 tonnes of CO2 eq. in total. Please see page14 for information on the composition and ecology of NBT PAVATEX woodfibre boards.

NBT PASSIVHAUS systemsA NBT PASSIVHAUS timber frame construction can accom-modate thick layers of thermal insulation without the need for disproportionately thick walls that consume valuable floor space. And the NBT system is flexible in its final finish: The NBT PAVACLAD system above is an external insulation system with cladding and the NBT DIFFUTHERM system below is an external insulation system with render.

NBT PASSIVHAUS systems are made of sustainable mate-rials and products, and occupants feel exceptionally com-fortable in A NBT PASSIVHAUS: Perhaps the biggest sur-prise is that daily life in a NBT PASSIVHAUS is absolutely “normal”.

PASSIVHAUS – From NBT PAVATEX

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Timber studs

NBT PAVAFLEX

PAVATHERM-PLUS

PAVATHERM-PLUS

PAVATHERM

Cladding orrainscreen

OSB (for racking, vapourcontrol and airtightness)

Plasterboard and skim

Service void

NBT PAVATHERM-PLUS+ orNBT ISOLAIR

Vertical battens(min. 40 mm for ventilation)

DIFFUTHERM

DIFFUTHERM

DIFFUTHERM

Timber studs

NBT PAVAFLEX

NBT 2-coat render system

OSB (for racking, vapourcontrol and airtightness)

Plasterboard and skim

Service void

NBT DIFFUTHERM

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09kg CO2/m2a eq.

Hardly any heating requirement!

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PASSIVHAUS – Comparison

Comparison is indicative due to range of possibilites of achieving standards

PASSIVHAUS

VentilationPassive stack or mechanical MVHR

Heat distributionNormal distribution Warm-air system possible

Low E glassDouble glazing Triple glazing

Insulation thickness> 190 mm > 300 mm

Renewable energyNot required Recommended

Heating requirement (Qh)No requirements

Usually 50 kWh/m2a

< 15 kWh/m2a

Air tightness< 3.0 m3/m2h < 0.6 m3/m2h

Electical appliancesMinimum A and A+ Usually A++

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VentilationTrickle vents Passive stack or mechanical

Heat distributionNormal distribution Normal distribution

Low E glassDouble glazing Double glazing


Renewable energyNot required Not required


Electical appliancesNo requirements Minimum A and A+

AECB silverPart L 2006

Primary energy consumption02 0


Usually 90 kWh/m2a

No requirementsUsually 50 kWh/m2a

Primary energy consumption

21 4kg CO2/m2a eq. 74kg CO2/m2a eq. 24kg CO2/m2a eq. Comparison is indicative due to range of possibilites of achieving standards

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The reduction of heat losses through the buil-ding fabric has been the subject of the Building Regulations for 30 years but still has a long way to go before an optimum level is attained.

It is considered that PASSIVHAUS and other equivalent stand-ards such as Minergie-P have reached the optimum level for building fabric. It should be noted however that different de-signs and in particular different climates will probably have dif-ferent optimums. The PASSIVHAUS standard has been devel-oped in Southern Germany where winter temperatures may stay below 0° C for many months and may commonly go as low as -20°C. Nonetheless the basic principles of insulation, minimising thermal bridging, and airtightness apply in all Eu-ropean climates.

Comparison between Part L, AECB silver and PASSIVHAUSOn this double page three energy standards are compared so that the differences between buildings can be clearly un-derstood, both in terms of the construction and in terms of energy use and carbon emissions in use. The three standards compared are:

• Building Regulations Part L 2006• AECB Silver Standard• PASSIVHAUS

AECB Silver standard is an intermedi-ary standard between current Building Regulations and PASSIVHAUS. It is cal-culated on the same principles as PAS-SIVHAUS, but does not take the energy reduction to the same level. Conse-quently it may be cheaper and easier to build, but will require a heating system and will have higher running costs. It is however a considerable step up from current building regulations

Comparison roof build-upsPart L 2006 (U-value < 0.30 W/m2K)

1. Roofing (tiles, slates etc.)

2. Counter battens 25 x 38 mm3. NBT ISOLAIR 35 mm

4. Rafter 100 mm & NBT PAVAFLEX5. OSB 12/15 mm (racking & airtightness)6. Service void 25 mm7. Plasterboard 12.5 mm, plaster, skim

and NBT emulsion paint

Comparison wall build-ups

1. 2. 3. 4. 5.6.7.

Part L 2006 (U-value < 0.35 W/m2K)

1. Cladding system (timber, brick screen)2. Vertical battens 40 x 40 mm3. NBT ISOLAIR 22 mm4. Stud 89 mm & NBT PAVAFLEX5. OSB 12/15 mm (racking & airtightness)6. Service void 25 mm7. Plasterboard 12.5 mm, plaster, skim


For more information please visit www.natural-building.co.uk 5

Comparison is indicative due to range of possibilites of achieving standards

PASSIVHAUS

VentilationPassive stack or mechanical MVHR

Heat distributionNormal distribution Warm-air system possible

Low E glassDouble glazing Triple glazing


Renewable energyNot required Recommended


Usually 50 kWh/m2a

< 15 kWh/m2a


Electical appliancesMinimum A and A+ Usually A++

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VentilationTrickle vents Passive stack or mechanical

Heat distributionNormal distribution Normal distribution

Low E glassDouble glazing Double glazing


Renewable energyNot required Not required


Electical appliancesNo requirements Minimum A and A+

AECB silverPart L 2006

Primary energy consumption02 0


Usually 90 kWh/m2a

No requirementsUsually 50 kWh/m2a

Primary energy consumption

21 4kg CO2/m2a eq. 74kg CO2/m2a eq. 24kg CO2/m2a eq. Comparison is indicative due to range of possibilites of achieving standards

21 0

Pleasant, PASSIVHAUS buildings are characterised by enormous energy savings and enhanced comfort for their occupants.

PASSIVHAUS (U-value < 0.14 W/m2K)

1. Roofing (tiles, slates etc.)

2. Counter battens 25 x 38 mm

3. NBT PAVATHERM-PLUS 120 mm

4. Rafter 175 mm & NBT PAVAFLEX

5. OSB 12/15 mm (racking & airtightness)6. Service void 25 mm7. Plasterboard 12.5 mm, plaster, skim


(other build-up options see page 14)

AECB silver (U-value < 0.15 W/m2K)1. Roofing (tiles, slates etc.)

2. Counter battens 25 x 38 mm

3. NBT PAVATHERM-PLUS 100 mm

4. Rafter 175 mm & NBT PAVAFLEX

5. OSB 12/15 mm (racking & airtightness)6. Service void 25 mm7. Plasterboard 12.5 mm, plaster, skim


PASSIVHAUS (U-value < 0.15 W/m2K)

1. 2. 3. 4. 5. 6. 7.

1. Cladding system (timber, brick screen)2. Vertical battens 40 x 40 mm3. NBT PAVATHERM-PLUS 100 mm4. Stud 140 mm & NBT PAVAFLEX 5. OSB 12/15 mm (racking & airtightness)6. insulated service void 50 mm7. Plasterboard 12.5 mm, plaster, skim


(other build-up options see page 14)

1. 2. 3. 4. 5.6.7.

AECB silver (U-value < 0.22 W/m2K)

1. Cladding system (timber, brick screen)2. Vertical battens 40 x 40 mm3. NBT PAVATHERM-PLUS 100 mm4. Stud 89 mm & NBT PAVAFLEX5. OSB 12/15 mm (racking & airtightness)6. Service void 25 mm7. Plasterboard 12.5 mm, plaster, skim


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Principle

A building envelope should be airtight when all ventilation openings are closed. The design requirement for air changes has to be provided by opening the windows manually, other controllable ventilation openings or suitable mechanical ventilation systems.

When assessing the air permeability of the building envelope, the following aspects must be considered separately:

• Individual building components must exhibit the necessary airtightness in accordance with building component standards

• The overall air permeability of the building envelope must meet the limiting and target values of building regulations

• Local air permeability (leaks, primarily on the inside) can lead to moisture damage because they allow moist interior air to infi ltrate the construction

• Local air permeability and associated draughts can have a detrimental effect on the thermal comfort of the occupants and can also lead to increased energy consumption

Air permeability

The air permeability of the building envelope is specifi ed by the ratio of surface area of the building to the hourly air exchange rate for a 50 Pa pressure difference. In Part L Building Regulations an air permeability of 10.0 m3/m2/h is allowed, for EST best practice for CSH level 3 an air permeability of 3.0 m3/m2/h, for higher CSH levels an air permeability of 1.0 m3/m2/h and for PASSIVHAUS an air permeability of 0.6 m3/m2/h are accepted as the maximum.

Design and construction

To ensure that the building envelope has the necessary degreee of airtightness, an airtightness layer is required over all parts of the construction on the warm side of the thermal insulation. Generally, the vapour control layer and airtight layer funtions are combined and provided by one membrane, sheeting or a board type material (OSB, multi-ply board, plywood, gypsum fi breboard, etc.). Such materials require fi xings and permanent air tight seals at joints and junctions in the form of adhesive tape, glue, mechanical fasteners etc., or may need to be held in place with battens.

Rock wool and glass-fi bre boards, wood fi breboards, wooden panelling, planking, acoustic linings, building papers etc. cannot achieve the degree of airtightness required for modern buildings.

The airtightness layer must be conceived at the design stage as a “seamless” layer over the entire building envelope, planned with its practical installation in mind, and shown as a separate layer on all drawings. Good planning includes

cor responding information in the tender docu-ments and detail in the working and fabrication drawings. The materials used to achieve the air-tightness must be sealed air-tight at junctions with adjoining elements such as windows, doors

and foundations. The installation of several layers each of which are only partially airtight will not result in a building with an adequate degree of sealing.

Testing

In order to achieve an airtight building envelope, measures and checks during construction and after completion of the building are necessary. If the airtightness layer has been properly designed and planned, expensive blower door measurements, leak detection by means of smoke tests or IR thermography, and unnecessary costs of repairs can be saved.

A properly designed and constructed building will fulfi l airtightness requirements without the need for further special work. NBT systems provide proper design and site support to ensure that the correct levels of airtightness are achieved.

w Sketch of the principle of an airtight-ness layer: Build tight, ventilate right.

PASSIVHAUS – Airtightness

For more information please visit www.natural-building.co.uk

Thermal BridgingHeat loss from buildings is a continuous process with energy fed in to maintain a temperature rise above ambient. The two main routes for this heat loss are ventilation (convective or air) heat loss and fabric (conduction) heat loss. The ventilation heat loss is addressed with an airtight envelope and MVHR. The fabric heat loss is made up from two parts:

Bulk area heat lossThis fabric loss was traditionally calculated by multiplying the area of external element (wall, roof, window, floor) by its U-value. The standards have clear instructions about how to do this to allow for repeating thermal bridges that occur within the elements: e.g. regular bridging of insulation by timber in timber frame buildings.

Geometrical thermal bridgesTaking geometrical or non-repeating thermal bridges into account means the inclusion of the extra heat loss from the junctions between the elements of wall, window, roof and floor. Each of these juncitons can be represented by a Ψ-value, which, when multiplied by the length of the junction, gives a fairly accurate measure of the extra heat loss to be added to the Bulk area heat loss above. This is represented as a y-value in the Building Regulations. Y-values for non-accredited details are rated as 0.15 W/m2K, for accredited details they are 0.08 W/m2K. For PASSIVHAUS very low y-values are required, typically 0.02 W/m2K.

The full thermal benefits of the NBT PASSIVHAUS systems are not immediately apparent to those who judge performance on the basis of quoted U-values. As the systems combine insulation across the structure, heat losses due to thermal bridging at junctions between walls, windows, roofs and floors are less than most other building systems.

NBT provides support for all the necessary thermal bridging details and calculations.

PASSIVHAUS – Insulation & Thermal Bridging

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InsulationIt is accepted in Europe generally that U-values of 0.1 W/m2K are the practical optimum. However, different design and different climatic conditions will have different requi-rements. The minimum U-value to achieve PASSIVHAUS standard is therefore < 0.15 W/m2K.

Your PASSIVHAUS home or office built with natural materials from NBT provides an outstanding thermal envelope but also a living environment at its best.

Effective cost and energy savingAlmost 90 % of the energy consumption in domestic house-holds is spent on heating and hot water. Up to two thirds of energy consumption can be saved in new bui ld -ings through appropriate thermal insulation: Energy-efficient building is recommended! The average consumption of new buildings with 100 m² living area is currently between 700 and 1200 litres oil per year. In contrast a PASSIVHAUS uses 150 litres maxi-mum.Source: Passivhaus Institut, Darmstadt

Saving through additional thermal insulation!

1. Roofing (tiles, slates etc.)2. Counter battens 25 x 38 mm3. NBT PAVATHERM-PLUS 80 mm4. NBT PAVATHERM 80 mm / NBT PAVATHERM 140 mm in

case false rafters are thermally disconnected as shown5. OSB 9/12 mm (racking & decking)6. Rafters 150 mm / NBT PAVAFLEX7. SIGA Majpell airtightness membrane8. Service void 25 mm or 50 mm insulated for improved

thermal performance 9. Plasterboard 12.5 mm, plaster, skim and NBT emulsion

paint10. False rafters 100 mm / NBT PAVAFLEX

w Junction detail roof with wall element. Note the large roof overhang to protect the façade

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PASSIVHAUS – Roof

Pitched roofsPitched roofs with insulation between and on top of the structural members are well established for PASSIVHAUS build-ups. This is mainly because of the following advan-tages: • The overall depth of the roof construction is less than

that of a system with only external insulation • The design of the inner surfaces does not depend on

the loadbearing structure• Detailing for minimal heat loss at wall junction is su-

perior

Construction and thermal bridgeA ventilation space is required between the roof covering and the secondary waterproofing layer (NBT PAVATHERM-PLUS+

sarking board), with appropriate air inlets and outlets at the eaves and ridge respectively.

The thermal insulation is laid between the members of the loadbearing structure, the air tightness layer and the va-pour control layer are on the inside.

To minimise the thermal heat flow through the structural elements the rafters end on the wall plate. The thermally disconnected false rafters are fitted onto a pair of noggins. All gaps are in-sulated.

AirtightnessPitched roofs with insulation between and over the struc-tural memembers lead to simple details for the airtight-ness layer and the vapour control layer at the wall/roof junction.

However, it is more difficult to accomadate components that penetrate the roof covering for architecural or struc-tural reasons, e.g. collars, kneebraces etc. The detailing at penetrations may cause problems and therefore such penetrations should be minimised if they cannot be entirely eliminated. NBT provide design support for roof insulationand airtightness detailing.

Roof and wall options:There are two basic options for the insulation layer within the roof and wall element:• Ecological: 150 mm of NBT PAVAFLEX. NBT PAVAFLEX batts are made of wood fibres and allow a vapour open construction

with excellent acoustic properties• Economic: 150 mm of Rockwool. Rockwool is made of melted stone that is pulled into very thin fibres. Mineral fibres are not

hygroscopic and therefore cannot store moisture etc.

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PASSIVHAUS – Wall & Ceiling

WallThe wall build-up is usually made of standard 219 mm tim-ber studs. To reduce significantly the heat loss through the studs bridging the insulation layer the whole building en-velope is wrapped with one thick insulation layer.

These layers are 80 mm thick to achieve a U-value of 0.14 W/m2K. To achieve lower U-values e.g. 0.10 W/m2K the wrapping layer onto the studs is increased to e.g. 120 mm and 50 mm of additional insulation is fitted within the service void (as shown in the drawing below).

The NBT PAVACLAD system The external façade is cladding (timber, brick, rain screen etc.) and the wrapping insulation layer is made of NBT PAVATHERM-PLUS+ boards.

The NBT DIFFUTHERM systemThe external façade is rendered breathable (lime-cement or lime render) and the wrapping insulation layer is made of NBT DIFFUTHERM boards.

CeilingThe detailing of the ceiling is important: Its load bearing junction with the wall should not lead to significant ther-mal heat loss and its acoustic properties must be excellent between rooms:

• The thermal bridge is greatly reduced by keeping the load bearing beams as short as possible in the wall. As shown in the detail below the beams penetrate the wall only by max. 140 mm and the gap on its face is insulated as well as the inside of the ceiling itself

• Impact sound is minimised through 30 mm of insula-tion underneath the flooring material and air borne sound through a heavy flooring material and insula-tion within the structural members

w Wall junction with ceiling and additional insu-lation in the service void

1. Cladding system (timber, brick, rain screen)2. Vertical battens 40 x 40 mm3. NBT PAVATHERM-PLUS 80 mm4. Stud 219 mm & NBT PAVAFLEX5. OSB 12/15 mm (racking & airtightness)6. Service void 25 mm or 50 mm insulated for

improved thermal performance 7. Plasterboard 12.5 mm, plaster,

skim and NBT emulsion paint

w Wall build up of the NBT PASSIVHAUS PAVACLAD system with additional insulation in the service void. Instead of the NBT PAVATHERM-PLUS+ with cladding NBT DIFFUTHERM with render can be used

1. Flooring system (wood, laminate etc.)2. Fermacell 2x 12.5 mm3. NBT PAVATHERM 30 mm (impact sound

insulation)4. NBT PAVATHERM-Profile 60 mm (air

borne sound insulation)5. Plasterboard 12.5 mm, plaster, skim and

NBT emulsion paint6. NBT PAVAFLEX Batts

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PASSIVHAUS – Floor

PrincipalsThe main purpose of a floor is to support the vertical im-posed loads and transmit them safely to the ground or supporting structure. It also needs to satisfy acoustic and superior thermal insulation, in addition to contributing to the overall stability of the structure.

Floor systemNBT PASSIVHAUS systems comply with both solid and sus-pended floor systems. However, suspended floors are gen-erally an economic solution for PASSIVHAUS buildings and thermally they have the advantage of having an air cushion underneath that insulates in addition to the insulation.

Suspended floorsThe ventilation of the space beneath the floor is provided through openings in the plinth running down in the exter-nal insulation layer. Most suspended floors are compatible with different piling systems. Foundation and flooring sys-tems are designed to individual specifications.

Thermal bridgeAs for all junctions of elements in a PASSIVHAUS build-ing it is of great importance to detail the joint between the wall and the floor very carefully to avoid thermal heat loss through this thermal bridge. The following detailing reduces the heat flow through the junction:

• External insulation runs over the face of the floor • Joists that run in the insulation layer are made of ma-

terials with a low thermal conductivity e.g. solid tim-ber or timber derivatives such as I-beams

• Floor joist bearing is kept as short as structurally possible

• Front of floor joist is insulated• U-value of floor < 0.15 W/m2K

PilingThere is an array of piling techniques that enables the de-signer to tailor the foundation systems to the needs. The techniques range from traditional driven piling, comprising driven concrete piles, driven tubular steel and combination piles, to vibrated or cast insitu piles. This kind of piling is ideally suited for contaminated land or inner city projects where removal and treatment costs can be prohibitive to development.

PlinthThe plinth area must be designed to avoid damage through water and/or discolouration of cladding due to water splash etc. The plinth starts 300 mm above ground level (area of water splash) and compromises the following detailing:

• Appropriate plinth insulation boards (XPS)• > 30 mm of ventilation entrance for NBT PAVACLAD

above plinth• If the plinth is brickwork the top brick is a plinth brick• If the plinth is rendered NBT HM 50 is used as base

coat in the plinth area

Please refer also to the NBT Timber Frame manual for NBT DIFFUTHERM details.

w Suspended timber floor with brick cladding on the façade in the splash water area

1. Flooring system (wood, laminate etc.)

2. Fermacell 2x 12.5 mm3. NBT PAVATHERM 30 mm 4. Vapour barrier / sheeting

(e.g. OSB 15 mm)5. NBT PAVAFLEX6. Vapour barrier / sheeting

(e.g. OSB 12 mm)

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PASSIVHAUS – Window

Thermally superior windowsWindows create the connection with the outside and they act like passive solar collectors. Since they also lead to en-ergy loss, especially in winter, it is important that in select-ing the windows the energy balance between usable solar energy and energy loss is considered.

Windows in PASSIVHAUS buildings must have a whole window U-value < 0.8 W/m2K.

Comfort criteria for windowsThe requirement for the windows of having a U-value < 0.8 W/m2K is not only based on the energy balance for the building but also on comfort: Because in PASSIVHAUS buildings there is no radiator heater below the window, the temperature on the window surface must always be above 17° C. Otherwise this cold air falls leading to a cold air spot on the floor making this area uncomfortable and also creats a real ris of mould.

Installation of windows and thermal bridgingThe installation of windows often leads to significant ther-mal bridges. To reduce the thermal bridge of the window it should be mounted central in the wall and the board where it is fixed to should not be persistent (see detail on the right).

Based on outside measurements, which is common for PASSIVHAUS buildings, typical thermal bridge coefficients (Ψ-values) for optimised window details are 0.03 W/mK because the sill does not allow the over insulation of the window frame. In the reveal and the lintel area the Ψ-value can be negative if the window frame is over insulated.

RollershutterInsulated roller shutters which are closed overnight, reduce the U-value of the windows to 0.3 W/m2K. If rollershutter are desired they should be fixed onto the surface of the wall and their operation mechanism should be air tight.

NBT can advise on window types and detailing and/or pro-vide recommendations of suitable suppliers.

w Wooden windows convey a feeling of warmth

1. Cladding system (timber, brick, rain screen)2. Vertical battens 40 x 40 mm3. NBT PAVATHERM-PLUS 80 mm4. Stud 219 mm & NBT PAVAFLEX5. PASSIVHAUS triple glazed window

(u-value < 0.8 W/m2K)6. Sill with up-stands

(triangle shaped gap underneath insulated)7. Nogging piece 60 mm /

NBT PAVATHERM 60 mm8. OSB 12/15 mm (racking & airtightness)

9. Service void 25 mm or 50 mm insulated for

improved thermal performance 10. Plasterboard 12.5 mm, plaster, skim and NBT

emulsion paint

Window options:• Beside having insulated glass, windows can have additional sound protection, burglar resistance or solar protection, and

windows with load bearing PU foam parts having a U-value < 0.7 W/m2K are also available• Wooden windows fitted with an additional protective aluminium on the outside are easy to maintain and are ideally protected

against wind and weather conditions

Cost Saving through additional

thermal insulation!

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PASSIVHAUS – Ventilation Systems

Airtightness in conjunction with a MVHR system keeps the warm air in and reduces the heating load of the house.

The addition of humidity control to the mechanical ventilation system can provide an environment in which dust mites cannot thrive. This will be of benefit to asthma sufferers.

Properties It is essential that the MVHR system is specifically sized and that the environmental and improved indoor air quality advantages are associated with all systems. If possible a system should be installed that is recognised or approved under Appendix Q of SAP 2005.

• Under normal circumstances a standard sized house is supplied by the MVHR with about 100 m3/h of fresh air to the living and sleeping rooms

• In special needs it can be set to a higher setting where between 160 and 185 m3/h is provided

• The same quantity of charged/polluted air is being sucked away in wet areas such as kitchen, bathroom and shower

NBT can advise on these issues and can provide consultancy support and/or recommendations of systems.

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© Bosco-von Allmen Monique, Studio d'architettura, Milano

w Possible timber frame structure and shape of a PASSIVHAUS building

Ventilation and heatingNBT PASSIVHAUS solutions can be considerably more airtight than conventional constructions, achieving air change rates smaller than 0.6 m3 per m2 at 50 Pa.

Healthy buildings require a minimum air exchange rate of 0.5 air changes per hour at 50 Pa. Therefore additional ventilation is a sensible and beneficial addition to a building constructed according to the PASSIVHAUS standard.

M e c h a n i c a l Ventilation with Heat Recovery s y s t e m s (MVHR) bring c o n t r o l l e d volumes of fresh air into all rooms of the building and remove a controlled volume of moisture laden or stale air to the outside. With the heat recovery system these units can recover heat from outgoing air to preheat the incoming air. This heat recovery can provide a large proportion of the heat required to keep the building at comfortable living temperatures. However, MVHR with integrated economic auxiliary heating is also available.

w The MVHR heating system provides al-ways enough fresh air and a healthy environment


PASSIVHAUS – Designers: Key Considerations

General:Team work in design and also construction is crucial. The following may be kept in mind:

• Support from NBT as partner is available at all stages of the process. NBT Consult is also available for de-tailed support or services and non-NBT products

• Compact building form: The ratio between the build-ing surface and the building volume should be as low as possible (dormers, bays etc. are better avoided)

• Building orientation: Typically the building is oriented toward the South where the façade of a PASSIVHAUS has many big windows. The North façade has only a few small windows. This leads to big solar gains

• To avoid overheating in summer the South façade should contain a sun screen.

Thermal bridges:U-values below 0.15 W/m2K require the prevention of ther-mal bridges. As the U-value decreases, thermal bridges be-come more and more significant:

• The proportion of timber over the whole cross-section should be minimised (timber conducts heat approx. four times more than insulation materials)

• Windows should be embbeded into insulation layer• The detailing at all junctions and joints (corners, win-

dows, doors, plinths, suspended floors etc.) requires special attention

• Simple architecture is favourable• Built in rollershutters should be avoided

Moisture control:Building practice dictates that the diffusion resistance of the individual layers must decrease from the inside to out-side. An effective vapour control layer on the inside of the structure (e.g. wood based products such as OSB etc.) re-duces the diffusion of water vapour. In combination with the vapour open NBT PAVATEX boards this ensures no damaging amounts of condensation build up within the construction (interstitial condensation):

• The vapour control layer must lie on the warm side of the thermal insulation

• The vapour control layer must cover the surface of the entire building envelope

The vapour control layer can be combined with other component layers, generally with the airtightness layer.

Airtightness:Thermally insulated constructions require a permanent air-tight layer on the inside:

• To avoid damage to the construction and to prevent heat loss the airtightness layer must be installed very carefully especially at junctions between components, at joints between elements, around penetrations of all kinds etc.

• Fewer penetrations will allow for simple, cost-effective construction

• Pipes and cables should not damage the airtightness layer in any way

The airtightness layer is more important than the va-pour control layer in terms of preventing damage to the fabric of the building.

Please refer also to the air tightness section on page 5 for further information.

Ventilation cavities:The primary function of ventilation cavities behind the cladding and/or the roofing material is to allow the airflow to carry away any moisture present by way of convection. The moisture is a result of vapour diffusion, precipitation or wet building trades is irrelevant.

Ventilated constructions (external walls with clad-ding, ventilated roofs) are regarded as favourable from a diffusion viewpoint, and do not require the diffusion behaviour to be verified by calculation, pro-vided the moisture loads do not exceed those equiva-lent to normal residential and working situations.

Services:The production of hot water is the component with the highest energy consumption in a PASSIVHAUS:

• Pipe runs should be as short as possible and well insulated. Dead legs should be avoided

• Pipes and cables must lie on the warm side (inside) of the insulation

• Low water appliances should be considered

Contractors:NBT has a network of trained contractors throughout UK and Ireland. Please contact NBT for information.

PASSIVHAUS – Physical Properties

14

Manufacture and ecologyNBT PAVATEX wood fibre insulation meets all ecological requirements from its manufacture to final disposal. The natural, renewable raw material for NBT PAVATEX boards consists of splinters and wood chips of native Swiss softwoods which are by-products from local sawmills. The wood’s own natural lignin, which already performs the function of a binding agent in the tree, is used as a binder, without the addition of further artificial binding agents.

NBT PAVATEX wood fibre board will remain effective as insulation material for the life of the building in which it is incorporated. It contains only natural materials and therefore can be recycled, composted or used to produce heat energy at the end of its life.

NBT PASSIVHAUS solutions for:Minimal thermal bridging

No separate heating system required

Excellent sound insulation and superior airtightness

Full system elements that come with design and site support

Highly vapour permeable constructions - no membranes needed

Cost savings through simple and robust construction that has few

skilled operations and is easily adapted for offsite manufacture

Exceptional heat storage for light weight structures

Warm inside surfaces of building elements and

thus improved well-being of occupants

Wall

Note: Calculations according to BS EN ISO 6946:1997 and BR 443. Studs assumed to be 38 x 140mm, 50 x 219mm or I-Joists (47mm flange and 9mm web) at 600 mm centres (allowances for sole plates etc, give a 15% bridging area for solid timber stud and I-Joist flange). Stud depth is taken to be the same as the thickness of insulation specified.

Timber stud dimensions 140 mm (with 50mm insulated service void)

219 mm (uninsulated service void)

245 mm (I-Joist) (uninsulated service void

Type of insulation on studs & thickness NBT PAVATHERM-PLUS+ / NBT DIFFUTHERM

NBT PAVATHERM-PLUS+ / NBT DIFFUTHERM

NBT PAVATHERM-PLUS+ / NBT DIFFUTHERM

100 mm 120 mm 100 mm 120 mm 100 mm 120 mm

U-Value [W/m²K] 0.15 0.14 0.13 0.13 0.12 0.11

Decrement delay [h] 12.5 13.7 13.6 14.8 15.3 16.6

1. Cladding system (timber, brick, rain screen)2. Vertical battens 40 x 40 mm3. NBT PAVATHERM-PLUS 100 / 120 mm4. Stud 140 or 219 mm / I-Joist 245 mm fully filled with NBT PAVAFLEX5. OSB 12/15 mm (racking & airtightness)

6. Service void 25 mm or 50 mm insulated for

improved thermal performance7. Plasterboard 12.5 mm, plaster, skim


1. 2. 3. 4. 5. 6. 7.

Rafter dimensions 150 mm 175 mmType of insulation on rafters & thickness over 100 mm PAVATHERM

PAVATHERM-PLUS+ PAVATHERM-PLUS+

60 mm 80 mm 100 mm 60 mm 80 mm 100 mm

U-Value [W/m²K] 0.13 0.12 0.11 0.12 0.11 0.11

Decrement delay [h] 16.7 18.1 19.4 17.6 19.0 20.3

1. Roofing (tiles, slates etc.)2. Counter battens 25 x 38 mm3. NBT PAVATHERM-PLUS 60 / 80 / 100 mm

4. NBT PAVATHERM 100 mm5. OSB 9 mm (racking & decking)

6. Rafter 150 mm & NBT PAVAFLEX7. NBT SIGA Majpell airtightness membrane8. Service void 25 mm or 50 mm insulated for improved thermal performance9. Plasterboard 12.5 mm, plaster, skim and NBT emulsion paint

Roof

Note: Calculations are done according to BS EN ISO 6946:1997 and BR 443. Rafters width assumed to be 50 mm at 600 mm centres (allowances for wall plates etc, give a 9% bridging area for the timber). Rafters depth is taken to be the same as the thickness of insulation specified.

PAVATEX boards provide an excellent carbon sequestration!


NBT ISOLAIR sarking boardWood fi bre board for breathable roof & wall constructions

Size: 770 x 2500 mmCover area: 750 x 2480 mmThicknesses: 22, 35 & 60 mmk-value / λD: 0.047 W/(mK)Density: 240 kg/m3

NBT DIFFUTHERM external wall insulation Wood fi bre board for rendered external wall insulation (EWI)

Size: 790 x 1300 mm Reveal board: 600 x1200 mmThicknesses: 60, 80, 100 & 120 mmk-value / λD: 0.043 W/(mK)Density: 190 kg/m3

NBT PAVATHERM-PLUS+ sarking boardComposite wood board for roof & wall insulation

Size: 780 x 1580 mmThicknesses: 60, 80,100 &120 mmk-value / λD: 0.043 W/(mK)Density: 180 kg/m3

Compr. strength: >70 kPa (at 10 % compression)

NBT PAVADENTRO internal wall insulationInnovative wood fi bre insulation board for refurbishment

Size: 600 x 1020 mmCover area: 590 x 1010 mmThicknesses: 40, 60, 80 & 100 mmk-value / λD: 0.042 W/(mK)Density: 180 kg/m3

NBT PAVATHERM general purpose insulation boardUniversal wood fi bre board for use in external & internal walls, fl oors & roofs

Sizes: 600 x 1020 mm & 1200 x 2050 mmThicknesses: 20 - 120 mmk-value / λD: 0.038 W/(mK)Density: 140 kg/m3

NBT PAVABOARD load bearing insulationWood fi bre board for highly insulated fl oors that have to carry loads

Size: 600 x 1020 mmThicknesses: 40 & 60 mmk-value / λD: 0.046 W/(mK)Density: 210 kg/m3

Compr. strength: >150 kPa (at 10 % compression)

NBT PAVATHERM-PROFIL wall & fl oor boardWood fi bre board for insulating fl oors or internal walls with plaster

Size: 600 x 1020 mmThicknesses: 40 & 60 mmk-value / λD: 0.043 W/(mK)Density: 180 kg/m3

Compr. strength: >70 kPa (at 10 % compr.ession)

NBT PAVAWALL external wall insulationWood fi bre board for rendered external wall insulation (EWI) for masonry substrates

Size: 600 x 800 mm Reveal board: 600 x1200 mmThicknesses: 80 - 160 mm (20mm increments)

k-value / λD: 0.040 W/(mK)Density: 155 kg/m3

NBT PAVAFLEX fl exible insulation battFlexible wood fi bre insulation batt for roofs, walls, lofts, fl oors & ceilings

Size: 375* / 575 x 1350 mmThicknesses: 40 - 240 mm (20mm increments)

Stock sizes: 50, 80, 100 & 140 mmk-value / λD: 0.038 W/(mK)Density: 55 kg/m3 * only stock sizes

NBT PAVATEX accessoriesNBT provides the full range of PAVATEX accessories & complementary products:

• NBT PAVATAPE incl. waterbased/solvent primers (for junctions on walls & roofs)

• NBT PAVATEX cutting blades & knives• NBT PAVATEX system glue (for sarking boards)

NBT ISOLAIR, all NBT PAVATHERM products & NBT PAVAFLEX are certifi ed by natureplus. This testifi es to excellent natural & ecological compatability.NBT PAVATEX wood fi bre insulation boards are manufactured in Switzerland according to BS EN 13171, have the CE marking and are monitored by 3rd parties.The following applies to all NBT PAVATEX products: Specifi c heat capacity c = 2100 J/(kg•K), Euroclass E (according to BS EN 13501-1), vapour resistivity µ = 5 (25 MNs/gm)

NBT Product Overview: Insulation

high performance systems NBT PAVATEX woodfibre systems provide exceptional thermal & acoustic insulation, summer overheating protection and moisture control for the whole building in wall, roof & floor

low carbon, renewable products NBT PAVATEX boards are made of waste wood & lock up the equivalent of ca. 11 tonnes of CO2 per building; raw material resources are entirely renewable, unlimited & FSC certified

healthy housing NBT PAVATEX insulation boards are certified by natureplus as non-polluting & the NBT systems lead to breathable constructions; NBT PAVATEX insulation is specified exclusively by the Sentinel Haus Institut for healthy housing

tried & tested systems NBT PAVATEX woodfibre insulation boards are widely used across Europe in all climates & conditions; physical values are 3rd party tested & guaranteed & production is according to BS EN

local service & support Pavatex‘s partner in the UK is Natural Building Technologies (NBT) who are a Technical Sales Company with nationwide coverage based in Oakley, Bucks. NBT lead the UK in sustainable materials & systems for high performance building shells

swiss quality & know-how for the UK produced & developed in Switzerland for more than 70 years by the the world‘s most innovative wood fibre insulation manufacturer

NATURAL BUILDING MATERIALS & SYSTEMS

Swiss Wood F ibre Insulat ion Boards.Natural Bui ld ing Mater ia ls .

Swiss Made

Natural Building Technologies Ltd.The Hangar, Worminghall RoadOakley, Bucks, HP18 9ULTel: +44 (0)1844 338338Fax: +44 (0)1844 338525email: [email protected]: www.natural-building.co.uk & www.pavatex.co.uk CERTIFICATE No 07/4448

PAVATEX SA

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110222 technical manual passivhaus

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