Attic Insulation & Venting
We are doing a roof tear-off on our brownstone so we can re-think all the insulation and venting to make it the most energy efficient. It is a flat roof, but has more of a slope then most. It has about four feet height in front going down to nearly none in back. We’ve read…
We are doing a roof tear-off on our brownstone so we can re-think all the insulation and venting to make it the most energy efficient. It is a flat roof, but has more of a slope then most. It has about four feet height in front going down to nearly none in back. We’ve read that electric attic fans are NOT the way to go (see: http://www.askthebuilder.com/236_Powered_Attic_Fans_-_Attic_Insulation_Facts.shtml ), but that maybe turbines with ridge vents are? It seems there may be different recommendations for flat roofs vs. pitched (which is what most articles are about). In looking through the archives here I’ve read everything I can find on attic vents, insulation, turbines, whole house fans, and others, but there doesn’t seem to be any consensus about brownstone roofs. We are looking for ideas to help our home stay cooler in summer and warmer in winter (beyond obvious get A/C and crank the heat).
If we do get non-electrical turbines is there some way to calculate how big a size we need (and how many vents for inflow?). Any recommendations for companies that do this welcome too!
Anyone faced this same problem and could share their pro’s/con’s? Whatever we do we also want to ensure there is no condensation build up possible in the attic area either.
Thanks!
I also used Federal Conservation, with fiberglass fill. For an 18 foot wide, typical townhouse, they put in two mushroom vents. One at each end of the roof, with tons of roofing cement to waterproof around the hole they cut out.
In retrospect, I think they overfilled. They filled the attic space FULL up to the underside of flat roof, instead of filling it to just few inches below the joists. Now I’m worried there’s no space under for the hot air to migrate to the mushrooms, but the guy did say that the heat would dissipate through the fibers and find it’s way out.
Electric fan would probably help, but I didn’t have the stomach for putting in another device.
My roof did not have as much height as yours, so I decided to insulate without venting, since there would have been minimal space for air to flow above the insulation.
I also had Federated come to check out my house but came to believe that they put in the vents in part to give themselves a big hole to work with when pumping in the insulation. Think twice about allowing them to cut big holes that could a source of future roof leaks.
I decided to go with Brooklyn Insulation, who works primarily with cellulose. They were excellent, fast, and less expensive. http://www.brooklyninsulation.com/
By the way, it appears that cellulose can handle crawl space moisture much better than fiberglass, which helped convince me that the venting was not necessary.
I would still like to get a “whole house” fan to vent hot air from the house through the crawl space, but that is a future project.
I haven’t tried this in a brownstone, but an unvented icynene roof is worth looking into.
http://www.icynene.com/
It is a great product.
Thanks Dave! I’ll give them a call now.
Also, in case anyone is searching in the future we found what appears to be a very good solution for flat roof ventilation when soffits (air intake) don’t exist on the roof. This system is designed specifically for flat roofs.
See link: http://www.roofvents.com/flat-rooftop-vent.html
It appears to be better than a turbine fan for many reasons (nothing can get in, no moveable parts (noise, breaks etc)) and it allows for passive ventilation in all weather. Just ordered it so fingers crossed. They were very helpful also in figuring out airflow calculation and what size to get etc.
If anyone has used this system I’d love to hear…
thanks!
Federal Conservation did mine…blown in non-treated fiberglass if I remember correctly. They also installed two vents. About $2,200 if I remember correctly. I think the guy’s name was Jim. He’s really helpful and will give you a lot of information.
It makes a big difference.
Even more so, if you have older skylights, and even newer replacements, put up a piece of plexiglass just below the light to add a layer of air insulation. It will make a big difference how much heat you lose through the single pane skylights