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Question DetailsAsked on 2/11/2016

Has anyone used UltraMax reflective attic insulation? Is it actually effective?

We were just planning to add extra blown in insulation to our attic, but we had a contractor suggest installing UltraMax as well. Is $4500 reasonable for 1300sf installed? It seems high for insulation, however, the heat barrier demo was pretty convincing.

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Below are links to several prior questions about that type product and related issues - more links to other similar questions under them and in the Home > Insulation link under Browse Projects, at lower left -

https://answers.angieslist.com/E-Shei...

https://answers.angieslist.com/Calcul...

https://answers.angieslist.com/How-co...

https://answers.angieslist.com/I-8-10...

https://answers.angieslist.com/Cellul...

https://answers.angieslist.com/Is-rem...

https://answers.angieslist.com/Averag...

https://answers.angieslist.com/I-blow...

Note that the normal light box demonstration is impressive, as it is intended to be - but is not directly analogous to your attic conditions, and also do not show the effect of normal insulation with an airflow barrier on top - usually use open unfaced batt insulation as the comparison.

Radiant heat barriers can be useful properly used - which it rarely is in attics, and improperly used (located wrong place in attic or used in attics that should not get it) can cause severe problems. It also has problems with trapping moisture under it so the attic has to be thoroughly sealed against air migration from the house to the attic to prevent that.

Also, the worst thing about it - typically it loses about 1/4-1/2 of its effectiveness in the first year from dust accumulation, which negates the emissivity - the heat reflection - abilities of the foil surface. And commonly becomes essentially ineffective in from 3-10 years - which negates the long-term potential cost benefits.

Some of the products are also so light-duty that they are commonly severly torn in installation, and can even tear in airflow through the attic in storms - I have seen it torn off in big sheets in outdoor windstorms.

There have been several university and EPA/DOE studies showing it is great initially when done right - though under-rafter installations (the most common) can significantly elevate the roof sheathing temperature, which is bad - and turns it into basically a pressure cooker situation if the sheathing or underside of the shingles are damp from a leak or condensation.

There is one product in use now that testing data may show promise for - blown-in foil strips, which are very economic to do, provide the thermal emissivity of the foil blankets, but does not significantly trap moisture, which might turn out to be a good buy - but too early to tell yet, and I am aware of only one independent study underway on it.

Done professionally under the advice of an engineer trained in thermodynamics and insulation it can save money in the very long run - or in a DIY situation, but I do not generlaly recommend it for residnetial applications because of the risk the contractor will cause a situation that makes thing much worse than they are now.

Also, because this is an eco-trend thing, contractors charge through the nose for it - typically $4-10/SF - when you can achieve the same net benefit in most cases for about $1/SF in added conventional insulation without much of the risks of moisture and overheating. So if you go through the economics, even assuming you stay in the house for a LONG time (average person moves about every 5-6 years BTW), at those prices it generally does not pan out. Even at a couple of $/SF it would not pay off for the general homeowner because you are not going to generally get anything more at sale time for having it, so while future homeowners MIGHT get long-term benefit from it, it is like a veary high efficiency HVAC system or ultra-insulated walls- generally the person who has it installed (or the initial homeowner on new builds) never sees any savings from the large capital investment.

Bottom line - generally, removing any blown-in cellulose insulation and replacing with vapor barrier as needed (commonlyu a thin layear of foam-in-place closed cell foam in retrofit applications) then fiberglass batt to the desired R-value, then overlaying with an inch or two of blown-in cellulose as an airflow retarder will achieve the same net result FAR cheaper, and with a system that does not trap moisture or cause overheating.

Answered 3 years ago by LCD




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