- Air Sealing
- Crawl Spaces
- Spray Foam Insulation
- Duct Sealing
July 1, 2016
These are some pictures I took during a home assessment I did yesterday on a home built in the 1960's. This shiny thing covering the floor throughout this attic is called a Radiant Barrier (RB). A Radiant Barrier is a low emissivity material, typically made from aluminum that is used to slow the transfer of heat - think of cooking with aluminum foil. RBs come in different forms, but they're often a thin foil like material, or applied to a thicker substrate of some-sort. You'll often see these in uninsulated areas where they are used to try and block some of the heat radiating through a material - Think POLE-BARN or a wind-shield cover for your car!
Now, besides being expensive, laborious and unproven, RBs can be installed in ways that make them ineffective, or worse, harmful. This particular application – laid over top the insulation in an attic - is potentially both.
Let’s talk ineffectiveness first. For radiant barriers to maintain their low emissivity and block that transfer of heat, they need to remain slick and shiny. Things like dust and grime cut down on the barrier’s ability to reflect heat and enable it to more easily pass on through. I don’t know if you’ve every messed with insulation, but it’s dusty and being in contact with it means you’re dusty too. Another issue with laying a radiant barrier down on a material is that it’s now in-contact with something else. This helps it to act less like a barrier and more like a conductor, actually helping to transfer heat into other materials.
Now for the double-trouble: This house is 5x as leaky as a new home, has never been air-sealed, and has bath-fans venting directly into the attic, under the radiant barrier. Since this barrier is installed on the attic floor, it’s essentially trapping any moisture exiting the house in the confined space between the dry-wall and the barrier itself. Particularly in the winter, condensation can get pretty bad here. It causes rot, mold, and it traps moisture in the insulation. Even without the radiant barrier, that moisture can still cause serious issues. I’ve seen plenty of moldy, totally rotted out rafters and roof sheathing. This system just exacerbates the problem.
The last thing you’ll see (maybe if was the first, idk) in these pictures is that the duct lines for the HVAC system are above the radiant barrier on the floor, meaning these lines moving the cold and warm air throughout your house are STILL in the hottest part of the attic. For my money, the only reason one should have a radiant barrier in their attic is to try to give the HVAC system a break. Even then the system is imperfect because during the winter, it blocks out heat gain from the sun that’s actually beneficial. Here though, the duct system runs right along the bottom side of the roof, so on a hot summer day, there’s only 2” of insulation between a 140 degree roof and the 55 degree air running through your duct system. That’s an 85 degrees difference and that is not good.
With the roughly $1 per Square Foot price tag that came with this faulty system, this homeowner could have sealed their house up, insulated their attic and duct lines, vented their bath-fans and had an actual pay-back period on their investment.
Please, remember to use only trained and certified contractors in your home. Experience in doing something incorrectly is no substitute for knowledge and only assures you’ll continue to get things wrong.
Your workers were very polite and helpful and did their work efficiently.