new method for attic sealing?


Old 05-05-09, 10:57 AM
Thread Starter
Join Date: May 2009
Location: Dallas, TX
Posts: 3
new method for attic sealing?

I'm a DIY-er but have never dealt with insulation issues. My new house (1958-era) has a 2000 sq. ft. attic that leaks like a sieve. There is some insulation between the joists, but most of the joists are exposed and the insulation is obviously inadequate. There is also no radiant barrier, which should be there to help with the hot TX summers. The attic is a short low-pitch attic, so it will be tricky to work in comfortably towards the edges.

I know that radiant barrier needs an air space to work effectively, so I thought of an idea that I have not seen discussed anywhere (although I might have missed this idea in my searches). The idea would be to deal with all of the air leaks and the radiant barrier by:

1. removing all of the insulation between the joists or at least making sure there is an air gap.
2. Putting plywood down over the joists that has radiant barrier attached to one side--the kind used for roofs--but with the radiant side facing down towards the air gap between the joists.
3. Sealing between the plywood sheets with foil tape, caulk, or something else.

I could then blow in insulation over the plywood.

It seems to me that this would seal all of the air leaks and put in the radiant barrier in an inexpensive and easy-to-install manner.

Would this work? Thanks for any advice.
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Old 05-07-09, 02:38 AM
Join Date: Feb 2008
Location: Lake Wales, FL
Posts: 463
You have two issues, one the heat leaking from the home during the winter through the fabric of the ceiling and through holes due to the suction effect of the wind.
The other the heating of the home during the summer due to radiation, convection and conduction - not helped by a shallow roof space.

The best solution is to dump the existing insulation and radiant barrier and spray in polyurethane foam or similar to a depth of at least five inches. (the more the better up to 12 inches)

The thing with sprayed in foam is, it will find its way into every odd shape in the roof and will seal every hole. It will solve the heat leakage during the winter and will remove the heat gain during the summer, well the heat gain from convection and radiation.

The heat moved by conduction through the fabric of the building will be attenuated but not removed.

To remove the heat conduction.To do this you would need to either: Cover the whole of the roof with five inches of polystyrene sheet and then lay a covering of reinforced concrete over to stop wind damage. This will stop the heat from the sun coming in but, by itself would not save the heat loss during the winter.
Or line the inside of the up stair ceilings and walls with two inches of polystyrene to stop the conducted heat through the fabric of the building, this will also help to stabilise the heat loss and gain.
Old 05-07-09, 03:00 AM
Join Date: Oct 2008
Location: New England
Posts: 9,990
"quick", I don't have time to reply completely, but I will give it a try by end of the dat.

"Perry" where I do like foam insulation in both spray and ridgid form, in the quantities you are suggesting, wow of course it will work, $20,000 to $40,000 for just the attic depending upon the going rates. I pay $1.05 per board foot, but have seen quotes here on the board over $2.00. Then you have to consider covering it with a fire barrier.

I'll be back.

Old 05-07-09, 08:24 AM
Thread Starter
Join Date: May 2009
Location: Dallas, TX
Posts: 3
Thanks, but let me be clear. I am NOT looking for the "best" way to seal the attic. I am looking for an inexpensive and fast way to seal and radiant barrier the attic myself. My method will cost under $900 for both and be fast compared to anything else. My question is, will it work? And if not, what is the next-cheapest and fastest good alternative?

BTW, the place is a one-story ranch. Thanks.
Old 05-27-09, 09:16 AM
Join Date: Feb 2009
Location: Maine
Posts: 7
The "cheapest" way would be to install unfaced R-25 over what you have now and really, really vent your attic.
Old 05-27-09, 09:30 AM
Thread Starter
Join Date: May 2009
Location: Dallas, TX
Posts: 3
Thanks, but that wouldn't give me the radiant barrier I am looking for. I'd like to both insulate and radiant barrier in the cheapest AND easiest way possible. And I like the idea above because it would let me walk through the attic easily without walking through blown-in insulation.

I'd love more responses!
Old 07-14-09, 12:49 PM
Join Date: Jun 2005
Location: Texas
Posts: 236
Buy the radiant barrier foil and install it yourself. You can lay it on top of insulation in hard to access areas or even do a hybrid insulation (staple onto rafters where you can and lay over insulation where you can't). Make sure to leave a 3-4" gap at top and install ridge vent to let air out. Get more insulation if you can see wood rafters on attic floor. 12-16" is ideal. I live in Wylie and did this last winter. You may even try Efficient Attic Systems. They advertise locally and will spray for $699 and will even add insulation. We have a 3500 sq. ft. home and elec. bills stay under $300 in summer. I did the rbarrier myself for about $300.

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