Spray foam insulation is by far the best for an attic. It is sprayed in the rafters areas and basically seals off the entire attic and stops the heat as soon as it enters from the roof. It can be very expensive though compared to regular fiberglass insulation or blow in insulation.
Christofer, There is a lot written about your particular condition. What I would do would be to install a spray polyurethane insulation (closed cell insulation) into the attic ceiling and down to and including the eaves. this installed over a 1/4" plywood that would be "cleated" down at a minimum of 1" below the bottom of the roof sheathing, thus eliminating the "hot roof" situation. As far as moisture... if you understand that warm air rises and carries the moisture up (another reason i would use a closed cell product) then it makes sense to foam any walls or kneewalls as well. The venting on the top side would not be to eliminate any interior moisture, but to make your shingles last longer (keep them from overheating). Quite a few asphalt companies have disclaimers on warrantees because of this issue. You would need to check with your steel roof manufacturer how they respond to a hot roof application.
Ok so you don't really want all that moisture collecting on your windows and or finished wall substrates in the attic. So an ERV/HRV or even the furnace fan run continuously would help distrubute or evacute the excess moisture if this is your main house furnace (air handler). FYI- change filters monthly in these systems to help mitigate possible mold issues. I recommend the 6" combustion air (bringing in dry outside air) code required in IRC. I am not sure if this furnace unit in your attic is the primary furnace (air handler) for the home. If so that would help distribute attic moisture to the lower parts of the home. If separate attic unit only, I'm not thinking it will ever distribute moist warm air to the lower level like you suggest.
Remember this... once you start changing the function of your home's ventilation/conditioned or unconditioning of a space you will be changing the whole dynamics of how the house used to function. Henceforth do your homework. All this said...I run my company business in the extreme temperature zone of Minnesota. Your local heating guys should have a better handle on providing a safe living environment for your family. Mold can be a serious issue.
We've done this application numerous times in southeastern PA with one subtle change, we use closed cell foam insulation directly against the underside of the roof sheathing. Open cell will continue to let air/humidity through, closed cell will not. Since air can't move through the closed cell foam there isn't any need for air flow under the roof sheathing because there won't be any humidity there to potentially condensate. Air already moves through the fiberglass insulation and that won't change when the Attic becomes conditioned space. I believe it would be best to remove ALL of the existing fiberglass ceiling insulation so that the Attic space becomes 'one' with the rest of the House. Fresh air intake to the fossil fuel furnace is necessary. It should be set up with a power damper that opens when the furnace turns on to allow combustion air directly to the heat chamber. When the furnace isn't running the damper is closed to keep unconditioned air out of the Attic.
Dennis D. Gehman, CR, MSA, CLC, CKBR, GAC, CAPS
President
Gehman Design Remodeling
NARI = National Association of the Remodeling Industry
CR = NARI Certified Remodeler
MSA = CertainTeed Master Shingle Applicator
CLC = NARI Certifled Lead Carpenter
CKBR = NARI Certified Kitchen & Bath Remodeler
GAC = Green Advantage Certified
CAPS = Certified Aging in Place Specialist
Foil backed plywood is the more efficient than spray. Here is one site but many use the same figures. http://www.atticfoil.com/install-questions/paint-vs-foil.html
The best thing you could do for your home to keep the warm in and the cold out is to 1st. check your insulation in your attic if your not properly insulated the heat will escape. Another is making sure your windows are secured and latched. and proper weather seal is on your doors so draft cannot come in.
You mentioned this room being over a crawl space. We have found that most spaces are incorrectly conditioned.....or should I say say, not conditioned at all. Insulation is typically installed within the floor joist, leaving the crawlspace open and unconditioned. The foundation walls and ground should have a vapor barrier installed over them and insulation should be installed around the perimeter. You wouldn't do the wall that connects to the main house. You want this space to be treated like an extension of the basement.
Depending on the application, spray foam is oftentimes preferable. Closed cell spray foam, applied properly, can also help reduce or eliminate the growth of mold, as long as it doesn't exist already. Spray foam is typically more costly, but has many benefits to include an excellent R value.
Are your heating & cooling bills going through the roof? Did you know that up to 40% of a home’s conditioned air escapes through the attic? Adding attic insulation is the most effective thing you can do to reduce greenhouse gas emissions.
Windows and doors are the largest culprit in lost of energy efficiency. It may not be the cheapest option but will provide you with the largest impact.
The best move would be to simply make sure the existing vapor barrier product is installed properly (flush to ceiling below) and add blown insulation over top to to get the best R value and at the least expense.
All of the answers given were great options. There are many, many ways to improve a home's energy efficiency. As we are a siding and window company, my focus will be on those areas. Windows are a huge energy loss/gain. Did you know that windows and doors account for approximately 50% of your heating/cooling loss? Air leaks around a window or door due to a crack of 1/16" of an inch is like having a hole in your wall the size of a brick. In the average home, that is equal to about 15 bricks. Consider how large that "hole" is in your home. The glass package is the most important thing to consider when replacing windows. Most folks just look at the cost of the window and install, and some smoke and mirrors some companies like to drag on about. A smart homeowner knows what Low-E is, what a good U-Factor rating is, whether or not it's single, double or triple pane glass, etc. etc. Same features apply to most doors. Lastly, siding is another area where a homeowner can save money. Check into insulated siding. Check to see what kind of underlayment is being applied to your home. Many companies don't even put a housewrap on to save cost and the average homeowner never knows. Make sure you only hire someone who is appropriately licensed and insured. Ask to see those documents. Hope this helps folks looking to replace siding, windows or doors! Happy remodeling!
Hello John,
STEP 1. This is a very common for homes with room(s) obove a garage. Replacing the window (s) in the bedroom may not solve your entire problem if the glass package you select does not include a high performance heat reflectant type glass. Which ever manufacturer you decide, its best to pay the additional cost and upgrade to thier best performance glass. If you have already invested in new windows then check your paperwork to see if there is a greater performance glass option you can upgrade with for that type window . This is a simple process and can greatly reduce your Solar Heat Gain for minimal investment.
STEP 2. Select a certified insulation professional in your area to provide you with a "critical point air seal". Properly applied by a certified professional at upper and lower rim joists in this room aproximatly 1' in width by 2" in thickness. Air sealing the upper and lower rim is a minimal investment and provides a significant and noticable change in comfort with a quick ROI. Consider this service for the entire home.
Warm regards
Colorado Home Exterior
Hire a structural engineer. This could be a bit more expensive initially, but you could stave off lot of frustration later.
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