I have a mansard roof with a parapet on the 3rd floor of my brick cavity-wall historic home (ca.1860). There is a hatch for roof access through the ceiling on the 3rd floor up to the membrane-lined parapet. Can I place some type of attic fan in the mansard roof to help alleviate the heat build-up in the roof rafter/attic area???
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Yes, as long as there is attic space above ceiling and it is sized for the volume of space in the attic. Also I think you will need additional vents at both ends of attic space so it doesnt cause a vacuum situation.Also you can add a ridge vent and soffit vents that will help also with heat build up.
Yes and try to vent from soffits and your ridge if you can.
This is a very good question. Typical vents or turbines are not designed for the vertical or nearly vertical pitch of a mansard roof. What we have done in the past to achieve energy efficiency here in Austin, Texas blistering temperatures is a combination of a radiant barrier with a custom designed metal peak cap.
What we have done is to borrow the perforated z-vent from standing seam metal roof systems and fabricate it into the metal which runs along the top of the mansard.
Typically an open hem and lazy cleat fastenening system works on buildings 2 stories and less. For every 10 feet of cap metal it will vent 1 square foot nicely.
You can use a high powered exhaust fan as well
Yes. It is possible. The esthetics would be the only thing you would want to take a look at ahead of time.
Roofing ventilation is a very important part of your roofing system. A powered vent is a great way to vent your roof. Make sure you get a power vent that fits your roof. Installing a power vent that is too strong and you will be creating a vacuum and will suck heat out of your home. Make sure you have enought air intake in you soffits. A power vent will only work if you have proper soffit intake. Do not mix power vents, ridge vents and gable vents. Installing two different type of ventilations can cause a leak and will not properly vent your roof. If you install a power vent and a gable vent then the power vent will draw air from the nearest place which will be the gable and not the eaves, you will vent only a part of the roof.
Your home in a historical area, should check with the historical comity at your city for there laws. They have restrictions to what can & can not be done to prevent them to remove and do it over. After make sure your roof has the proper vents, ridge vent, vented drip edge & facia. Then hire electrical contractor to make sure the job is done safe, take out a building permit.