Attic Mylar insulation?

Reply

  #1  
Old 02-26-16, 01:59 PM
E
Member
Thread Starter
Join Date: Mar 2013
Posts: 50
Received 0 Votes on 0 Posts
Attic Mylar insulation?

When the wife and I were looking at houses, one of the houses we were looking at had a new roof and they put material that had mylar backing to improve the insulation properties of the roof.

I was wondering if anyone had retrofitted their roof to add a mylar backing?

I know in college one of the engineering professors was in ASHRAE and he went and put aluminum foil behind all the rafters and supposedly really helped out his summer AC bill (Houston TX)
 
  #2  
Old 02-26-16, 03:15 PM
B
Member
Join Date: Oct 2008
Location: New England
Posts: 10,524
Received 37 Votes on 34 Posts
Hi EL,
In the deep south or any other air conditioning dominated climate a good way to keep a house cool is to never allow the solar energy in. That can start with shading to keep the sunshine away and then with selected shingles or other surface that reflect much of the radiant energy before it can heat the roof. Once the roof gets hot that energy has to cross the void of your attic. It has 2 modes of transportation, radiant energy and convection. It is the radiant energy that a foil surface below the roof can reduce. Some new homes down there actual use a plywood decking that has a layer of foil on the underside.

Be careful of exaggerated claims as the foil industry does have problems, but w well informed home owner can benefit from a properly installed radiant barrier.

Bud
 
  #3  
Old 03-01-16, 12:41 PM
E
Member
Thread Starter
Join Date: Mar 2013
Posts: 50
Received 0 Votes on 0 Posts
When I used to live in New Mexico and had a flat roof, I used that elastomeric reflective coating on the roof and it really helped, but now that Im back in Texas and have an attic again I was thinking that there must be some way to improve the energy efficiency given that I have such a larger volume of air space between my ceiling and the roof now (I HATE flat roofs...)
 
  #4  
Old 03-05-16, 09:55 AM
N
Member
Join Date: Oct 2003
Location: San Diego
Posts: 687
Received 1 Vote on 1 Post
Hi El,

as a matter of fact I just did that with my roof project. Roofer was very resistant to install the radiant barrier, but I insisted and he ended up installing it.
Unfortunately I don't have concrete data for you that proves or disproves the RB distributor's claims because the dates I measured the temperature of the roof (from the inside out, my drywall and insulation is partially removed as well) were different temperatures and amount of cloud cover, so no really way to compare.
I can tell you for sure there is something to it, because when I went up on the roof on many occasions during the install and I felt the radiation reflected on my face and body pretty strongly after the RB was installed, before the roof went on.
I also added a RB/fiberglass insulation sandwich inside my attic where we felt the most heat was emanating from, so we hope that works too.
Everyone (professional) says that most important in energy saving effort is either creating air conditioned space in your attic or sealing attic from your living area to prevent warm/cold air leaks from one place to the other. I also suspect that it's the last thing people tackle because it's so hard to do right and/or expensive to do if you hire someone.
 
  #5  
Old 03-05-16, 10:54 AM
N
Member
Join Date: Oct 2003
Location: San Diego
Posts: 687
Received 1 Vote on 1 Post
Should I install rigid foil faced foam insualation here?

I had to remove part of the drywall and insulation in my living rood because of the water leak.
I very rarely had to use the little access door for the coax and phone cables on the other (exterior) side of this wall, but when I did I hated fumbling around the insulation.

Is it a good idea to add a piece of a 2" rigid foam insulation right behind the door and fill the rest of it with fiberglass?
I realize, there's nothing wrong with rigid foam except maybe there is. The stuff I have has foil on both sides so when I started figuring out how best to put it in, it downed on me...
Would it possibly start interfering with coax cables? Yes it's shielded, but there is a lot of data flowing through it and it's a lot of foil around it.
Good/bad or don't matter?

Thanks!
 
  #6  
Old 03-14-16, 01:17 PM
E
Member
Thread Starter
Join Date: Mar 2013
Posts: 50
Received 0 Votes on 0 Posts
I dont think it will interfere with the coax.

there has to be a signal for something to interfere, so there would have to be something flowing through the foil.

but then again I am a Mechanical Engineer and just assuming.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: