For all you 'flat-roofed modernists' out there; how do you, or do you even, vent the joist space (type V residential) on flat roofs especially at soffit overhangs. Moderate climate like socal...
We drill holes in each joist every so often to allow for airflow between the joists. We then put vents under the soffits wherever possible. You can also use a foil-lined osb sheathing to help reduce the amount of heat build-up in the roof
tell the builder to put that in writing and have them assure the client that he/she will take care of any roofing membrane de-lamination problems / mold issues in the roof
don't listen to your builder on this one. if the roof is insulated, it must be vented. our building code calls for a min. 1-1/2" cross strapping above the joists to facilitate air flow. i like to use discreet continuous perimeter sofft venting, tucked into the wall/sofft intersection and then do additional venting at the edge of the soffit, using a more "designed" pattern of holes and bug screen (of course this all depends on your soffit material). if you have no overhangs, you can vent through the parapets, or use roof vents.
you may as well accept the fact that you will see the vents and make them look pretty...better to have some vents on your building than a fucked up roofing system and a leaky building
If you plan on drilling holes in the joists and you are using TJI's you will have a problem because hot air rises and will pocket above your drilled cross-vent holes causing condensation. We have done one of two things.
1. Use Icynene (or equal) insulation and fill the entire cavity so that there is no air to vent. Or,
2. Design your roof assembly so that the insulated panels are above your roof joists, effectively making the roof joists part of the conditioned space.
Jun 29, 07 7:02 pm ·
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Venting...
quite literally.
For all you 'flat-roofed modernists' out there; how do you, or do you even, vent the joist space (type V residential) on flat roofs especially at soffit overhangs. Moderate climate like socal...
Any feedback is mucho appreciated...
poke 2 holes in it
silverlake
if you dont vent the roof, you are STUPID.
We drill holes in each joist every so often to allow for airflow between the joists. We then put vents under the soffits wherever possible. You can also use a foil-lined osb sheathing to help reduce the amount of heat build-up in the roof
just like a baked potato...
mdler, I know.
I got a builder tellin' me forgettaboutit because theres no attic...
silverlake
tell the builder to put that in writing and have them assure the client that he/she will take care of any roofing membrane de-lamination problems / mold issues in the roof
don't listen to your builder on this one. if the roof is insulated, it must be vented. our building code calls for a min. 1-1/2" cross strapping above the joists to facilitate air flow. i like to use discreet continuous perimeter sofft venting, tucked into the wall/sofft intersection and then do additional venting at the edge of the soffit, using a more "designed" pattern of holes and bug screen (of course this all depends on your soffit material). if you have no overhangs, you can vent through the parapets, or use roof vents.
thanks for suggestions mdler and njp...
going to vent - looking to do it as inconspicuously as possible...
silverlake
you may as well accept the fact that you will see the vents and make them look pretty...better to have some vents on your building than a fucked up roofing system and a leaky building
you can use structural insulated panels (SIPS) or Corebond(TM) the entire assembly...
batts need vents
Depends upon the assembly.
If you plan on drilling holes in the joists and you are using TJI's you will have a problem because hot air rises and will pocket above your drilled cross-vent holes causing condensation. We have done one of two things.
1. Use Icynene (or equal) insulation and fill the entire cavity so that there is no air to vent. Or,
2. Design your roof assembly so that the insulated panels are above your roof joists, effectively making the roof joists part of the conditioned space.
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