have you added radiant barrier spray paint? (West, Howe: new house, roofing) - Dallas - Texas (TX) - City-Data Forum

loves2read · 10-31-2008, 09:13 AM

anyone had this done to a house you bought?

we bought one that is only 4 yrs old but no radiant barrier decking under the composition shingles...so reroofing will never help to get it done...no trees for shade--but there are no windows on west side of house and only two facing south...so won't be much heat gain from them...
has two stories and fiberglass insulation--not blown cellulose or foam...

would it be better to live there for a year to check our bills

I know that most people who have had spray done--if done correctly--have noticed improvement in comfort levels even if bills were not that much less with rising energy costs...

getmeoutofhere · 10-31-2008, 09:34 AM

I have not personally had it done, but I know several people that have, and they saved the $600 or $700 it costs to have it done back within the first year.

One guy I work with had it done and said his summer electric bill went from about $750 to $500 or so.

FalconheadWest · 10-31-2008, 09:40 AM

My parents had it done in 2007 to a house built 2006 and they noticed about 40% change and they're a one story house.

Several of my clients have done it and say it makes a big difference of keeping the house warmer in winter and cooler in summer, but I've only got numbers from one of my clients and they saved about 30% summer to summer and that was an 8 year old house.

We scheduled to get it done, but then got relocated so we didn't. We're putting the tech shield into the new house.

And I'm not sure what size house getmeoutofhere is talking about, but the costs my clients told me, from what my parents paid, and from what my own estimates were, the costs ranged from $1800-3200 to get it done properly. If it was only $600-700, I think everyone would be doing it, but it's more expensive than that.

lh_newbie · 10-31-2008, 09:50 AM

The spray radiant barriers only block 25-30% of the radiant heat. Getting a company to come and staple a thin sheet of radiant film (looks like tin foil) to the roof rafters blocks about 90% of the radiant heat.

Because of this, most "spray radiant barrier" companies also include blowing in about 6" more insulation. From what I have seen, the insulation actually is doing more good than the spray barrier.

Outside barriers and additional insulation, it's very important to look at ventilation in the attic. Are your soffit vents properly spaced and sufficient to let "cool" air into the bottom side of the attic? Do you have ridge vents or power vents? Are they sufficient to let the hot air out?

IMO, it's really a three pronged approach: add insulation, get a good radiant barrier and ensure proper venting.

Those three items will make a tremendous difference.

FYI: I am a total geek on measuring things... and we do NOT have a radiant barrier (yet). Yesterday, when it was 79 degrees out, at about 2:30, I used my IR thermometer, pointing it under the West facing roof decking... it was 109 degrees. If it were 90 degrees out and mid summer (hotter sun), we're talking easily hitting 125 degrees... We do have a continuous soffit vent (was installed recently, didn't have it during this last summer) which should help our AC bills. We also finished up adding about 13" of insulation to our attic (had only 2" of insulation before). Last summer, our 1976 home (South windows and roof shaded by a tree) cost us $276 for the peak month of electricity (1443 KwH that month, rates shot up something crazy) and it's 2576 sq ft. Keep in mind we did have a 16-SEER air conditioner installed as well. So we've done the following: (1) insulation, (2) ventilation and (3) high efficiency A/C. This winter, I am planning to climb up there and begin installing a radiant foil insulation myself. I can only imagine with all four items completed what our cooling bills will end up like next summer...

Before we did the insulation, new A/C or ventilation, we had a bill for only 2-weeks in Sept '06 that used 1,560 Kwh (would have been > 3,000 if we lived here the whole month). Compare that to the 1,443 for July '08 and you can see we clearly HALVED our bill. I definitely contribute the largest savings to the AC unit.

Brian

getmeoutofhere · 10-31-2008, 01:36 PM

Quote:

Originally Posted by FalconheadWest

My parents had it done in 2007 to a house built 2006 and they noticed about 40% change and they're a one story house.

Several of my clients have done it and say it makes a big difference of keeping the house warmer in winter and cooler in summer, but I've only got numbers from one of my clients and they saved about 30% summer to summer and that was an 8 year old house.

We scheduled to get it done, but then got relocated so we didn't. We're putting the tech shield into the new house.

And I'm not sure what size house getmeoutofhere is talking about, but the costs my clients told me, from what my parents paid, and from what my own estimates were, the costs ranged from $1800-3200 to get it done properly. If it was only $600-700, I think everyone would be doing it, but it's more expensive than that.

I think he just did his attic only. I may be mistaken on the cost, but I swear he said about $600.

loves2read · 10-31-2008, 02:53 PM

I read on Angie's list several people say that it was about $1 per sq ft of attic roof to spray

I agree that the radiant foil is better blocking--but don't think people can get into this attic to do that well enough to really cover the space--think spraying would be easier to do...
some of roof line is pretty irregular...
don't know why they did not put in the tech shield...would have been so efficient--insulation alone is not enough...

kamiller42 · 10-02-2010, 10:08 AM

I hate to bring back an old thread, but this is one of many here which touched on this subject. So rather than create a new one, I will use one of the existing.

I have read again and again how foil barrier is better than spray on. It is true the effectivity of the foil it rated higher than spray. However, someone told me the high rating for foil is true only if installed right on the roof decking, which isn't possible due to all the nails protruding on an existing house. The foil sits off the wood and the effectivity is reduced to 60-65%. Spray on isn't affected by protruding nails. It sits right on the wood, and you get all its effectivity.

So it sounds like foil is great for new homes or when getting a re-roof, and spray on is good for everything else. Sound right? Was I be fed a line about material to surface contact affecting effectivity?

Mister Nifty · 10-02-2010, 02:02 PM

Quote:

Originally Posted by kamiller42

I hate to bring back an old thread, but this is one of many here which touched on this subject. So rather than create a new one, I will use one of the existing.

I have read again and again how foil barrier is better than spray on. It is true the effectivity of the foil it rated higher than spray. However, someone told me the high rating for foil is true only if installed right on the roof decking, which isn't possible due to all the nails protruding on an existing house. The foil sits off the wood and the effectivity is reduced to 60-65%. Spray on isn't affected by protruding nails. It sits right on the wood, and you get all its effectivity.

So it sounds like foil is great for new homes or when getting a re-roof, and spray on is good for everything else. Sound right? Was I be fed a line about material to surface contact affecting effectivity?

You don't want spaces between the foil and the inside of the roof as that could cause mold. I would think the material needs to be smashed tight against it. My younger brother, usually a brilliant fellow, foolishly nailed insulation beneath his house underneath the floor of it. Well, heat tends to rise as cold tends to fall, so it isn't necessary to do this. Instead, he got a lot of mold because of the moisture build up.
(After building an igloo, Eskimos learned to dig a hole in the snow inside to trap the coldest temperatures downward in them)
Thinking about it logically, the sides of a house aren't any further away from the sun than the top of it. The reason it gets hotter towards the afternoon when the sun is higher in the sky is because radiation from it heats up the earth's atmosphere with this being enhanced by bodies of water(which causes the warm up and cool off times to lag). Yet, the radiation should also have an effect on the sides of the house during the times of sunrise and sunset when the sun is facing them. In other words, even though it is cooler during those times when less of the earth's atmosphere is exposed to the sun, the direct sunlight will still be radiating heat into the house.

kamiller42 · 10-02-2010, 05:39 PM

Looking back on my message, I think I should have said "emissivity" instead of "effectivity."

skids929 · 10-02-2010, 06:58 PM

Good topic here...I am from NE where Ridge vent and continuous soffit vent is the norm in anything constructed in the past 20 years or so. The idea up here is to basically keep the roof the same temp as the outside..Most homes I have seen in Texas do not use this method, not sure why. Seems like they vent with Air Hawks and vents of this type, which leads me to my point.. I can't imagine stapling radiant barrier to the back of your rafters and deflecting that heat back out at the roof, while essentially trapping it in the depth of the rafters without some sort of effective venting system that vents the entire roof. Can you staple it directly to the back of the sheathing instead of the rafters? I would imagine trapping heat like that shortens the life of the shingle considerably. Which leads me to my question..

Aside from hail storms, what part of the roof fails prior to a Texas resident getting full life out of the shingle? Does the shingle just basically burn up? Here in NE we get about 25-30 years out of a properly laid roof, how about in Tx?