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Question DetailsAsked on 2/28/2018

Does anyone have any experience using Progressive Foam Technologies Fullback Insulation System? Pros and Cons?

We are replacing our current Vinyl Siding for a house built in the early 1990's. The house was not wrapped during construction. We want to have the house wrapped with Tyvek and also add an insulation layer and we saw the Fullback Insulation System as well as Alside's Prodigy product.
We also thought of using Tuft-R as an option for the insulation layer (if its cheaper than the other 2).
Are there other options available? How effective is adding an insulation layer to a home? Do they install Tyvek first, then insulation over that? Thanks.

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You can find some previous questions about foam insulation under lap siding in the Home > Siding link, under Browse Projects, at lower left. Nothing specific about that brand that I recall.

BTW - instead of Tuft-R I think you meant Dow Tuff-R polyiso insulation board ?

Generally speaking, lap siding is NOT waterproof - it is a water-shedding system, but a fair amount of water gets in behind it, so the house is best protected by spacing it off the house wall with battens or similar spacers to provide an airflow and drainage gap, then a water-shedding "housewrap" barrier under that which also acts as a draft barrier while still allowing some moisture release from the house wall if it is higher humidity and/or warmer than outside. Therefore, if you provide a drainage gap behind the siding, that also means airflow there behind the siding - so that is a poor place for insulation (especially in winter), though it is simple if bonded to the siding - albeit not very effective because that is also thin, and mightly expensive relative to the R value you get from it.

The best place for insulation from outside temperature extremes - because the joints tend to not be totally watertight or airtight - is behind the housewrap, either inside the wall (conventional studbay insulation or foamwall construction) or over the outside of the studs (board facing). That eliminates the heat losses (or gains in summer) due to convective airflow through or over the insulation - also able to easily get substantial insulation value, rather than the very small R value available from the foam-backed siding or folding-sheet foam panels being sold to go on/behind siding. Getting it inside the wall construction also reduces flame spread and foam combustion poisonous gases/smoke issues - because foam-backed siding has the same issue as the Grenfell Tower fire in London where the clad-foam insulation had phenomenal flame spread.

As for effectiveness - $ for $ good weatherstripping/gap filling draft control through the walls and around windows and such is pretty much always the lowest cost and best return on your $. Attic insulation upgrades from the normal R-11 to R-16 up to more like R-30 to R-60 depending on climate is commonly the next most cost effectvie - mostly because installation cost is cheap due to easy access.

From there on, your normal 2x4 studwall has an R value (resistance to heat flow) of about 15 give or take, windows generally (give or take some) have an R value of roughly 1 per layer of glass - so R=1 for single pane, about 2 for double-pane, 3 for triple-pane, generally 5-7 for higher-tech windows though it is possible to get up to about R=15 to 20 with 5 layer windows with xenon gas between the panes/films.

So - commonly square foot per square foot enhanced window insulation would seem the next logical place to look - but because windows are expensive per square foot and typically less than 10% of total wall space, overall insulation enhancement on the general wall usually is the next best energy measure after attic insulation. The point at which added insulation is worth it varies by area, obviously worth the most in very cold climates with high heating bills, or hot or sun-baked areas where air conditioning costs are high, and of course the poorer the current insulation the better it looks.

Generally speaking, about 1/3 to 1/2 of a normal house energy loss/gain is through the walls - and R values are additive, so doubling the R value of the wall (say from R-15 with R-13 studwall fiberglass batt) to R-30 by adding about 3 inches of EPS insulation (like Dow Hi-40) would cut that 1/3 or 1/2 share of heat loss/gain by about half - or about 1/6 - 1/4 difference in overall HVAC operating cost, which for a typical size and insulation house would be on the order of $150-500/year in energy savings - significant, but does not go real far in paying for added insulation.

But generally, you are talking minimum 15-20 or more year payback periods on energy savings for major insulation jobs - though of course while residing is a cheaper time to do that because the siding is off anyway. But generally, unless you spend money to change current shoulder-mount windows (typical, with outer frame overlapping the siding) to flush-mount or recessed ones or are replacing the windows anyway, adding thick insulation to the outside of the walls can be pretty expensive because of the cost of resetting all windows and doors over the "pushed out" new siding and extending interior frame and molding to match the now-thicker wall. This leaks some people to the more expensive and less effective foam-backed siding and/or folding foam sheets.

One thing to pay attention to is not getting a double vapor barrier situation in your wall, which can trap moisture from any leakage or condensation inside the wall. Tuff-R has water-barrier quality surfaces and is a very tight foam so acts as a vapor barrier (when properly joint seamed), so if your house has the typical vapor barrier behind the interior drywall I do NOT recommend using that. Some vendors and contractors will say - fine, just put it outside the Tyvek and firring strips - but then you have an airflow behind it, which is not a bad thing if protecting against exterior heat but makes for a lot of convective heat loss from the wall behind it in cold winters. In fact, in cold winters, a quite substantial amount of the insulation is ineffective due to airflow behind the insulation if on the "outside" of the standoff air gap.

Also, I recommend spacing be provided behind the lap siding, to allow for free drainage and evaporation of water getting through it, else you can get mold formation there - a very common thing with sidings applied directly to housewrap or insulation. Read up a bit on Rainscreen wall concepts - the up and coming solution to the extreme wall mold issues that have developed over the last 20 or so years with "tight" houses and exterior foam insulation. Unless in a very cold or hot area, adding insulation during residing is generally going to have a payback period of at leat 10-15 years, so makes some sense (especially if energy rates are high or you figure they will go up dramatically in the future) if this is your "forever" house, but otherwise not so much.

The calculations are straight-forward but confusing to most people, so commonly when thinking substantial house insulation upgrades, it is best to get an Energy Audit done - which will identify not only locatiuons where insulation will be most cost-effective, but also identify air loss locations which can usually be very cheaply remedied.

Answered 8 months ago by LCD

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