What is minimum requirement for the insulation of a mobile/manufactured home according to the HUD-code?
Sunday, February 17, 2019
The HUD-code for mobile homes is primarily a “performance" code, rather than a “prescriptive" code, meaning pretty much what it sounds like: instead of specifying what to install and how to install it, the code sets performance standards that give the manufacturer some leeway in how they choose to meet the standard.
The insulation performance standard is a U-value, also referred to as a Uo value, which is the overall coefficient of heat transfer through the envelope of the home. The map above shows the U-value requirements for the three thermal zones that HUD has mapped for their standards. A lower U-value number means better insulation.
But most people are more familiar with R-value, which is the opposite of U-value, and a measure of the resistance of a substance to thermal transmission. It is also the inverse of U-value, so 1 divided by the U-value equals the R-value, and a higher R-value means a better insulation rating.
Unfortunately, the conversion is not quite that simple since the U-value represents the transfer of energy through both conduction and radiation (which is why it often used for rating windows that have multiple different components with varying thermal transmission rates), while R-value represents only resistance to heat transfer. But the R-rating approximately correlates and is what most people understand, so here’s the conversion to R-value for the three zones: Zone 1 = 8.62 R, Zone 2 = 10.41 R, Zone 3 = 12.65 R.
There are also several additional requirements:
1) The installed heat equipment, combined with installed insulation, must be able to maintain minimum 70º F interior temperature (CFR 3280.5061).
2) Cavities in exterior walls, floors, and ceilings must be provided with thermal insulation [CFR 3280.5061(b)].
3) Homes manufactured for Zone 3 must have storm windows or insulated glass windows [CFR 3280.5061(c)].
Also, see our blog post How energy efficient is a mobile home?
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