Ask Your Question

Angie's List Answers is the trusted spot to ask home improvement and health questions and get answers from service companies, health providers and consumers. For ratings and reviews on companies in your area, search Angie's List.

Top 30 Days Experts
Rank Leader Points*
1 kstreett 240
2 Guest_9020487 110
3 Guest_9190926 105
4 GoldenKid 100
5 ahowell 95
6 KnowledgeBase 95
7 skbloom 80
8 Guest_98024861 70
9 Guest_9311297 70
10 Guest_9400529 70

*Updates every 4 hours

Browse Projects By Category

Question DetailsAsked on 10/4/2013

how good is reflective insulation

Do you have the same question? Follow this Question

2 Answers


I have installed it off and on over several decades. My experiences are outlined in a blog on my website.

Jim Casper Old Energy Conservation Guru during Pres Carter's Era

ps It did zero good for winter conservation


Answered 6 years ago by jccasper


You don't say what application you are considering - I will assume you are talking insulation, not window reflective films, which work well on sunny side windows but do have limited life before they start peeling, so are not really a permanent solution unless integrated into the interior of a triple-pane window system like HeatMirror.

1) in walls it is essentially useless (little better than regular batt), because for the reflective material to work, it has to be exposed to a free air surface, not in contact with anything. It works by reflecting radiated heat (like heat you feel from the sun, a fireplace, or baseboard heater) back out. Therefore, it has to be exposed - like in an open attic, to reduce heating from hot attic in the summertime. In a wall, it will be in contact with another material, so there is almost no radiative heat transfer occurring - it is all conductive, like the heat from a burner to a pan, or from a hot surface to your hand when you touch it.
2) in attics it can reflect summer heat back up and reduce air conditioning costs, but you have to be careful, because, being a film, it also acts as a vapor barrier in the winter, trapping warm, moist air in the insualtion and promoting mold and icing - sometimes even to the point of ceiling collapse in poorly sealed houses in very cold areas. Therefore, the right place to put it would be in free air above the insualtion, with ventilation between the two - pretty much impossible to do in a truss-supported roof, though can be done in a rafter supoported roof by fastening onto the underside of the rafters, and providing ventilation both below and above the layer.
3) some people are putting it on the underside of their roof in the rafter spaces, wrapped around the rafters from space to space. In my opinion, this is just plain wrong - first, the barrier if placed against the sheathing is in contact, so there is no radiation reflected to speak of. Second, this insulation location keeps roof heat in the summer from radiating from the sheathing into the attic where it can be vented through roof or ridge vents. Third, this puts the sheathing and moisture retarder in extreme heat so they degrade fast, and any trapped moisture becomes a mold farm, I have seen roofs that were collapsing from the trapped moisture rotting rafters and sheathing.

Answered 6 years ago by LCD

Related Questions

Terms Of Use
Privacy Policy