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OK so its not so old - 1982 brick one story, 2500 sq ft, 3 bed 3 bath in Texas. We replaced the original HVAC system with 21 seer condensers, variable speed 80% AFUE furnaces and added insulation in the attic to bring it up to an R38 rating. The insulation guy informed us today that unfortunately we need some more work since the house was built for a wood roof and has soffits spaced every 8 feet. Since it now has an asphalt shingle roof it needs 13 more soffits installed and 2 more turbines (already have 2 on the highest roof of house) to move the air around. So, I'm stumped. This isn't a huge amount of money but I'm just surprised that the HVAC guys (who hired the insulation guy to do the work) did not mention anything about soffits and turbines. Anyone know about this kind of thing??
A House built in 1982 should not have had a wood roof on it. I believe the code had already changed but I'm sure someone else will know for sure. There are a lot of factors to determine proper ventilation and it will save a lot if it is done properly. My house (1958 construction), was upgraded last year and my electric bill dropped almost $100 during the summer.
A good site to start your research is:Department of Energy - Your Home
Turbines are ok but must have sufficient soffit to work with them, ridge vents and soffits are great too. Some vents cannot be installed together as they will circumvent each other depending on the way the house is constructed, i.e. ridge vents and gable vents. There is a lot of info on the internet if you google it.
Thanks for the response. I'll check out the site. I'm trying to get this home as energy efficient and possible ( at reasonable cost!) and am finding a lot of misinformation out there. We had 6 quotes before we got our HVAC system and a few of the companies recommended things that are totally against energy effeciency - getting bigger than necessarry Condenser units since 'more is better', etc.
Have the heat load calculation done on the house, if your AC or furnace is oversized you will pay for it. Also, I would have gone with the 90% furnace.
Ok, so you are in TX and have a major AC problem in the summer. Having been in TX in the summer I can understand.
One of the best things you can do is build what is called an under roof air flow system. This is a super good investment for the money. Is cheap to build.
Basically it is forming channels right under the roof, usually using the roof rafters to create a duct to trap all the heat before it has a chance to heat up the attic volume. These systems normally do not require any fans or forced air flow if done correctly. Fresh air is allowed to flow in from the outside, usually thru soffit vent area, flow thru the under roof area, then is vented by some means. Roof ridge vents are great or you can build a collection area at the roof peak and vent that area by some means. Natural circulation type air flow should be sufficient in most cases. There is a height differential and the heated air flows very nice due to differences in density.
I had a huge problem in the summer in OH in my present shack because of the way the house was built. Is an old 1923 shack that I remodeled. Before it got so hot in the upstairs area it was impossible to live without AC. I built an under roof air flow system and it solved the problem. Now don't use any AC in summer.
I like the stuff called Reflectix which is an aluminum foil type bubble wrap that has super insulation quantities if proper understood and installed correctly. I used it to build the under roof air flow system and vented the system via a roof ridge vent. Some of the best money you can spend. Reflectix is not that expensive, easy to install. You must have an air gap on both sides of it for it to work properly. Has a high working temp up to 160F. An under roof system is a dynamic cooling system, not static like normal insulation, it can really save you huge amounts of money, especially if you are in a normally hot summer climate. Home centers like Lowes sell Reflectix, it comes in varying widths.
This is the better mouse trap. In general you are never allowing the attic volume to get much hotter than the rest of the house. The Reflectix is such a super good insulation that it contains most of the heat coming thru the roof and vents it in a collected type system before the problem occurs.
There are a number of ways to build a under roof air flow system. The general idea is always the same. Isolate the roof decking area from the rest of the attic volume. Establish an air pathway thru the system channels to collect the heat, provide a vent path to the outside. This requires some method of providing cooler air to the vent system. Normally this is by some type of soffit vents but there are also many other ways that it can be done.
Benefits are.
1. It is quite low cost and easy to engineer. Especially if the roof rafters are presently exposed.
2. Normally no forced air / fans, etc are required in a properly built system. You should not even need things like roof turbines, etc.
3. The overall attic temperature will stay quite comfortable.
4. Reflectix is also a super good insulation. You can achieve something like R-18 with just one layer. If multiple layers are used, each must have an air gap on both sides.
5. The air flow thru the system will vary with temperatures involved. The hotter it is, the more air flow that will result in a natural circulation type system.
6. Nothing is complicated or needs any type of sensors, controls or clap trap.
7. It works very, very well. Every new house should be required to have a well engineered and install under roof air flow system. There are even methods to tap into such a system for aux winter heating or heat / preheat domestic hot water. Once you experience the results from a good system it can make a believer out of you. Just web search on the general subject for a bunch of ideas how various type systems can be built. Always the same idea, trap the heat coming thru the roof in some type of channel / duct work type affair and vent it. The better methods like mine will have the collection system also be a super good insulation. Reflectix is only one way to build a system.
8. Probably the best return on the money of anything you can do in terms of cutting your AC bill. Proper venting of the heat and prevention of heat build up on a daily basis in the attic area also is very good to prolong the roofing and general house structure working life too.
What a great post Cosmic, "low-tech" solutions like what you described are my favorite. I would add this is the perfect time of year to install an under roof air flow system or any other project in the attic, before the heat makes it too miserable to be able to work up there.
What a great post Cosmic, "low-tech" solutions like what you described are my favorite. I would add this is the perfect time of year to install an under roof air flow system or any other project in the attic, before the heat makes it too miserable to be able to work up there.
Good point. Plus you have to think about the access available. I had to build a catwalk system in the attic before I could do the under roof system. No floor in the attic and it was too difficult to mess around laying in all the insulation. Can't even stand up, only a crawl type space. Doing when not hot is the only way to go. I will want one of those systems in every house I ever own. Just the cat's meow if done correctly.
Location: Sometimes Maryland, sometimes NoVA. Depends on the day of the week
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I have heard of various ways to channel air from your soffits to the ridgeline through channels and such - just like Cosmic talks about. But, we don't have a ridge vent and I'm kind of nervous on the thought of cutting up my roof to add one. Right now all we have is an attic fan in the gable on the north side of the house. I'd love to hear more about ways to cool my roof and/or attic - cause what we have no isn't working that well.
I'll second the Reflectix idea, but I'm not familiar with that exact application. A radiant barrier would be a good choice for you. Cheap enough and worth a try. I've heard good results from it.
A House built in 1982 should not have had a wood roof on it. I believe the code had already changed but I'm sure someone else will know for sure.
There is no code violation for a shake (wood) roof. The only thing that has changed regarding shake roofs is the shingles have to be chemically treated for fire resistance.
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Under roof air flow system
