gould evans aim high-roof ev… · – roofs 49 green roofs • to save energy, use white roofs...
TRANSCRIPT
Building Science Roofs
John Straube, Ph.D., P.Eng
presented by www.buildingscience.com
This presentation
• Roofing – Low-slope – Pitched – Membrane, metal, etc.
Building Science .com
–Roofs 2
Roofs
• Roofs are significant proportion of the area of low-rise buildings – Significant to total cost – Major area for heat loss / gain – Low-slope membranes usually need
replacement every 15-25 yrs. • Wide range of membrane choices • Insulation on top or bottom of membrane • Green roofs = organic ballast
Building Science.com Enclosures No. 3 /
Building Science 2008
Joseph Lstiburek – Roofs 4
Gould Evans/The Garland Co Roofs April 7, 2011
Straube © buildingscience.com 1 of 13
Building Science 2008
Joseph Lstiburek – Roofs 5
Building Science Enclosures No. 6 /
Building Science .com
Roofs 7
Inverted Roof
• Pros: – Preferred approach – Exterior insulation
eliminates thermal bridges
– Protects membrane • Cons:
– Added weight of ballast
– Can only use XPS
Building Science 2008 Enclosures No. 8 /
Gould Evans/The Garland Co Roofs April 7, 2011
Straube © buildingscience.com 2 of 13
Exposed membranes
• Pros: – Lightest weight – Wide variety of
insulation and membranes
• Cons: – Exposed membrane!
Building Science 2008 Enclosures No. 9 /
Building Science .com
– Roofs 10
Sloped roofs
• Basic Physics are the same • Slopes allows non-waterproof materials to
be lapped “shingle fashion” • Air – vapor impermeable insulation needed
OR ventilation of the sheathing
• Air leaky roofs require more ventilation
Building Science – Roofs 11
Building Science.com Roofs 12
Gould Evans/The Garland Co Roofs April 7, 2011
Straube © buildingscience.com 3 of 13
Building Science 2008
Joseph Lstiburek – Roofs 13
Building Science .com
Roofs 14
Building Science
– Roofs 15
Building Science 2008
Joseph Lstiburek – Roofs 16
Gould Evans/The Garland Co Roofs April 7, 2011
Straube © buildingscience.com 4 of 13
Building Science 2008
Joseph Lstiburek – Roofs 17
Building Science 2008
Joseph Lstiburek – Roofs 18
Building Science .com
Roofs 19
Building Science – Roofs 20
Gould Evans/The Garland Co Roofs April 7, 2011
Straube © buildingscience.com 5 of 13
Building Science.com Roofs 21
Building Science 2008
Joseph Lstiburek – Roofs 22
Building Science – Roofs 23
Building Science 2008
Joseph Lstiburek – Roofs 24
Gould Evans/The Garland Co Roofs April 7, 2011
Straube © buildingscience.com 6 of 13
Building Science.com Roofs 25
Building Science 2008
– Roofs 26
Building Science – Roofs 27
Building Science – Roofs 28
“Money spent on roof slope is one of the best bargains in the construction business” Wayne Tobiasson, CRRL
Gould Evans/The Garland Co Roofs April 7, 2011
Straube © buildingscience.com 7 of 13
7
Building Science – Roofs 29
Building Science – Roofs 30
Building Science – Roofs 31
Combine multiple penetration at doghouses
Building Science – Roofs 32
Avoiding penetrations is always best
Gould Evans/The Garland Co Roofs April 7, 2011
Straube © buildingscience.com 8 of 13
Parapets
Building Science – Roofs 33
Building Science 2008
– Roofs 34
Building Science.com Roofs 35
Rain leaks at parapet Air leaks everywhere Heat leaks everywhere
Building Science.com Roofs 36
Gould Evans/The Garland Co Roofs April 7, 2011
Straube © buildingscience.com 9 of 13
Building Science.com Roofs 37
Building Science – Roofs 38
Building Science .com
Roofs 39
• Air barriers and fully-adhered membrane
Building Science
– Roofs 40
Gould Evans/The Garland Co Roofs April 7, 2011
Straube © buildingscience.com 10 of 13
Low-level air barriers
• Roof membranes can be air barriers • In practise, a deck level air barrier is more
reliable, easier to control – Other benefits include secondary roof during
construction and re-roofing
Building Science .com
Roofs 41 Building Science – Roofs 42
A cheap air barrier
Building Science – Roofs 43
White roofs: the coming storm
What air barrier
White roofs
• Lower heat gain • Reduces drying out of roof • Require better moisture control!
– Air barrier – Construction moisture
Building Science.com Roofs 44
Gould Evans/The Garland Co Roofs April 7, 2011
Straube © buildingscience.com 11 of 13
Green Roofs
• Green roof acts as thermally massive, low solar absorption surface – Not insulation
• Save energy compared to black roof of same R-value
• White roof with more insulation is less expensive alternate
• Don’t feel good
Building Science 2008 Green Buildings No. 45/51
“Perfect” Green Roof
Building Science Green Buildings No. 46/51
Fully-adhered membrane!
Energy: Dirt is not insulation
Building Science.com 47
Source: Ray, S., Glicksman, ASHRAE Buildings XI 2010
20 R10 30
Stormwater Management
Building Science Green Buildings No. 48/51
NRC Roof Test Ottawa, Canada !” (19 mm) rainfall over 6.5 hrs 150 mm soil over membrane
Gould Evans/The Garland Co Roofs April 7, 2011
Straube © buildingscience.com 12 of 13
Building Science – Roofs 49
Green Roofs
• To save energy, use white roofs with lots of insulation
• Soil does store lots of stormwater – Retention mats can do the same
• Likely cleans water somewhat • Likely absorbs particulates
Building Science No. 50/51
Building Science.com Roofs 51
Building Science
Roofs 52
Gould Evans/The Garland Co Roofs April 7, 2011
Straube © buildingscience.com 13 of 13