Attic Insulation

Instrument 41 · 10-15-2013, 11:22 AM

Has anyone here installed radiant barrier insulation in their attic against the rafters? Looking at this option but have heard that it can increase the heat to the shingles??

masraum · 10-15-2013, 11:42 AM

I read the same thing. There seems to be a bunch of conflicting info out there about the radiant barrier stuff. I'd rather get a solar attic fan.

A930Rocket · 10-15-2013, 01:54 PM

I'd be weary of what the reflected heat would do to the rafters, roof decking, and shingles over time. Good insulation and air flow goes a long way to keeping it cooler.

gshase · 04:20 PM

I own a business that does spray foam insulation and I have doubts about R.B. That said most shingles are manufactured wall above 450 F and a high temperature in an attic is 185F. Either with either foam or R.B. the temperature increase is 8-12 F according to GAF and ELK shingles manufactures. My doubts are with the spray on R.B. The solar shield on the back of the roof decking lowers the temperature around 35F on a sunny day.

Instrument 41 · 10-15-2013, 04:19 PM

I have looked into foam for this house but the price is more than I can afford right now. My utility bills aren't high but looking for more "stable" conditioned air.

gshase · 10-15-2013, 05:06 PM

I tell my customers to place a remote reading thermometer mid way in your attic and track it for a few days in the peak heat of the day. Temperature above outside air temperature in PERFECT attic is 10-15 degrees, That being said many I see are 50-65 degrees hotter than outside air. Many times this can be lowered with ventilation. Passive like ridge and soffit vents can help. Solar tube makes the best solar attic fan I have seen, 1200 CFM of air with no wiring is pretty good @$350.

masraum · 10-15-2013, 06:56 PM

Quote:

Originally Posted by gshase

Solar tube makes the best solar attic fan I have seen, 1200 CFM of air with no wiring is pretty good @$350.

Good to know. Thanks

Instrument 41 · 10-15-2013, 07:44 PM

This solar tube, it would vent out of a turbine vent?

masraum · 10-15-2013, 08:08 PM

Quote:

This solar tube, it would vent out of a turbine vent?

I'm guessing solar tube is the brand name of a company that makes solar posted attic fans. They usually go in the spot that a turbine would go.

Groesbeck Hurricane · 10-16-2013, 04:15 AM

Wife insisted on it but it is installed as part of the underlayment below the metal roofing and above the wood seperated by tar paper. Seems to be working well in our installation.

We found 4x4 sheets of industrial fiberglass and foam to install as insulation. This is what is used in industrial buildings. Ours was the leftovers and we bought cheap.

VincentVega · 10-16-2013, 04:18 AM

I believe he's referring to this fan company, Solar Star Solar-powered Attic Ventilation Systems | Solatube

Air sealing with tape, caulk or spray foam and a healthy dose of insulation goes a long way. Not expensive and DIY in most cases if you are interested. I used blow in fiberglass in my new place, much cleaner installation than my previous experience with cellulose. I got everything from HD.

fireant911 · 10-16-2013, 05:32 AM

We had this (radiant barrier) done to our house just last week. Yes, it does increase the heat at the shingles; however, those change are rather small (around 5 degrees). From the homework I did prior to choosing this approach, the benefit of using radiant barrier is mostly realized by areas in the south. Along with the radiant barriers, baffles were installed followed by the the insulation. One of the benefits I discovered while researching the radiant barriers is the increase in R values realized by using the radiant barriers optimized. Although the radiant barriers themselves offer no R value, the addition of the radiant barrier to insulation increases the R values of the insulation. For example, R-13 insulation used in conjunction with a radiant barrier increases the overall R value to R-21... likewise, R-19 becomes (as my memory serves me) an equivalent of R-28.

http://www.radiantguard.com/studies/TVAPerformanceTesting.pdf (old but worth reading). I read several more that were NOT from the manufacturer's website as they are often somewhat skewed. Radiant Barrier | North American Renewable Energy Directory NARED

The difference we felt was incredible. Note: this project was for a garage/attic addition to our house (24' X 40' garage with a 10' X 40' room above the garage). I can shoot some pictures if you are interested.

Por_sha911 · Por_sha911's Garage

Wouldn't a solar fan increase heating cost in the winter by drawing in outside air and lowering the attic temp? If you want to improve your utility costs year round, you need a fan that can be shut off in the winter.

gshase · 05:43 AM

Yes Solar Star is the correct link. Now they have a 1600 CFM one. 15-30 min. to install. I put 2 on MIL house and they run for an hour after sunset. They run @ a low speed in the winter, less sun but a remote switch is an option.