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Radiant barrier???

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Old 07-28-2008, 06:18 PM
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hey pc , how does that radiant heat work in concrete floors? i saw a episode on it , seemed to be the way to go with a concrete slab home , they had also did the counter tops in concrete and ran smaller tubes so the counters were warm in the winter..
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Old 07-28-2008, 06:56 PM
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Originally Posted by CIGARETTE 1972 View Post
hey pc , how does that radiant heat work in concrete floors? i saw a episode on it , seemed to be the way to go with a concrete slab home , they had also did the counter tops in concrete and ran smaller tubes so the counters were warm in the winter..
Its great when installed properly like anything else.It costs alot of money to do it right.Alot of guys just put as much tubing they can into the slab and hope it works.The best way to install it is to have the rep/engineer do a heat loss calculation and design the system for your particular house.Multiple zones,different floor types can make a big difference.You can also run antifreeze through the system in the event of a boiler going down,you wouldnt have any frozen pipes. Moderate temp doesnt create alot of exspansion so it works great in gypsum based concrete flooring where heat will flow evenly throughoput.

I used to sell hot water boilers,domestic storage tanks for hot water,and hot water coils (hvac) and a combo of radiant.It saved all that baseboard and radiator crap .You already have central air going in a house why not utilize the ductwork for heat as well.

Im now retired from PLumbing thank god!
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Old 07-28-2008, 07:13 PM
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Originally Posted by gerritm View Post
http://efficientattic.com/the-energy...FQiNHgodWlNaSg

These guys are doing the most advertising locally. The barrier sounds like it might work along with the insulation, but you have to remove residual heat from the attic and that is why you need enough air vents to get the hot air moving (convection) out of the space. I agree with Plumber's Crack ( being a plumber by trade I can relate), the foam is a good idea and it is something you can do yourself.
Gerrit,that is the company that came out and gave us the qoute.
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Old 07-28-2008, 07:28 PM
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A radiant barrier is a great investment in TX during new construction or when it is time to re-roof. The incremental cost for foil backed sheathing when you are installing sheathing is only $200-300. Retrofitting a radiant barrier is difficult in a low slope application and is can be expensive....$1500-2500? Watch out for the Tin Man.
Done correctly you can significantly reduce the heat load with a radiant barrier even in a well ventilated attic. A drop in attic temp from 150 degrees to 120 is very possible. Ventilation is huge, turbine vents and 12X12 static cans are not work the $. You want a continuous ridge vent and continuous soffit vents. As electrical cost will likely continue to climb at a rapid rate, these improvements along with a new 15+ seer HVAC system are all good long investments.
Assume you could reduce you cooling cost with a R/B 10-15% and that your electricity cost increase is 5-7% a year. Run the numbers a see if you like the payback. Your local electric supplier should be able to give your some better numbers on the estimated % savings with a R/B.
I would also suggest asking the contractor if he would allow you to visit a job that they are doing so you can see if you like his work.
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Old 07-28-2008, 09:33 PM
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I like the idea of the foam, but didn't do it in my house because I couldn't justify the cost difference at the time. (It was 3x conventional insualtion) Plus, I had some concerns. Not sure if anyone has mentioned it yet or not, but the foam insulation makes the attic space, un-vented so in a retro-fit there's a couple of extra steps that need to happen. I.e. soffits and roof vents need to be closed off. Basically your attic becomes an a/c'd space which is why the temp will stay within 10 degrees of the house. A big concern I would have, especially on a retro-fit, is the condition of the roof sheathing. The foam is sprayed directly to the underside of the sheathing between the trusses. Therefore if there is any signs of rot or you need to replace the roof a few years down the road, it may cause a problem.

The cheapest way to go is going to be upgrading your existing insulation and adding a radiant barrier. If you add the foil radiant barrier that is stapled to the underside of the roof rafters and upgrade the insulation to an R-30 I would imagine you'd see a signifigant savings in cooloing costs.

I would definitely prefer the "stapled" radiant barrier to the foil-backed ply because the barrier attached to the rafters creates an air space with circulation and allows the hot air to travel up and through existing ridge or off-ridge vents. Also, make sure if you go with a radiant barrier they do it in the entire attic space, not just over the a/c space.

To give you an idea on energy costs, my house is 2500 under air and 4000 under roof. I have R-30 and a foil radiant barrier and with a 12 seer a/c and a programmable stat my electric bill last month was $220. I live in FL and have (2) full size fridges, a chest freezer and (2) water heaters.
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Old 07-28-2008, 09:50 PM
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be sure and check them out, there have been a lot of scams and shoddy work involving 1/ siding 2/ insulation 3/ windows in Houston over the past 20 years. I would suggest using Home depot contractor services if you cant find a good BBB report on any one else, at least they will make it right.
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Old 07-28-2008, 10:06 PM
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We build and remodel buildings and houses. Go with what plumbers crack said to do he is telling you the best way. If done radiant barrier not much change.
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Old 07-29-2008, 06:21 PM
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Call your local Homebuilders Association and get their contractors directory. The Insulation Contractors in that directory will not be the fly by night snake oil salesman that typically sell radiant barriers. Call a few Homebuilders in the directory and ask who they use. Drop that Homebuilders name when you call the Insulation Contractor.

In my experience the foam insulations in a roof assembly should be left for new construction only. The entire house must be designed from the start to work with the insulation package. To work properly you must seal the entire structure. This is not likely to be possible on a house built in the 1920's. The house needs to be designed to operate in a sealed enviroment with no gas burning water heaters or furnaces in the attic. You will have to run a/c ducts and a return air in your attic. Your roofing material will also have to endure a higher heat load thus reducing its life. There are some gains to be had when doing a complete foam job but these gains are not possible to acheive just retrofitting an attic.

Typically we see 16 seer two speed a/c units on foam houses that are sized smaller than normal. This is where most of the gains come from. The unit is sized to run almost constantly on low speed then on high when needed. An accurate heat load calculation on the house is required to size the unit correctly. Too big a unit you wont get the savings. To small and you cant cool the house on hot days.

All that being said the best thing in your situation would be to reinsulate your attic and make sure you have plenty of attic ventilation. In Houston I would recommend R-30 to R-49. Depending on whats up there now you should be able to get this done in blown fiberglass for less than $1.00 per square foot on the area to be blown.

Before any insulation is added you should take this opportunity to take care of any maintaince issues in your attic and run any speaker wires, tv cable, cat5 computer cable, or the like. When the insulation contractor is done everything will be covered up and you will damage the insulation digging in it to find something.

I cannot stress how important it is to have plenty attic ventilation. Every house is different but you need to make sure you get PLENTY cool air in from the soffits and PLENTY of hot air out the top. Install extra soffit vents, ventilate porch ceilings, add turbins, ridge vents, power ventilators. Whatever it takes.

Radiant barriers on a properly vented attic will have only a limited effect. Retrofitting an existing attic is an expensive proposition with limited gains.

Ron Cardinal
President
Ascension Insulation & Supply, Inc.
Insulation Contractor since 1987
Owens Corning "Certified Energy Professional"
"Enviroments For Living" certified
[email protected]

Last edited by rjcardinal; 07-29-2008 at 06:24 PM.
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Old 07-29-2008, 07:00 PM
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Ron,
Great post, very will said. When are you going to start buying from RIS? I didn't know you were a performance boater.
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Old 07-29-2008, 07:22 PM
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Thanks for all the info guys I guess i need to mull this over and talk to some contractors.
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