Our house has no insulation inside the walls.
It has foil-faced polyiso board installed under the siding - R value of approx.7.20/inch. Nothing but air inside - which has an R-value of 1. If I use this table, the R-value of our walls is currently:
Outside air film - 0.17
Siding, hardboard - 0.34
Foil-faced polyisocyanurate board - 7.20
5/8" plywood - 0.77
3.75" air (old studs) - 1.00
1" plaster - .45 x 2 since it doesn't have plaster in the table
Inside air film - 0.68
Total wall R-value = 11.06 That's not awful. University of Central Florida says wall insulation is not that critical for Florida.
InsulAdd paint coatings says their products can increase the effective R value of a wall by 20%, which would beFor a cost of $175.00/5 gal./250 sf/gal for the RBC Radiant Barrier Coating, applied as primer, and $130.75/5 gal. /275 sf for the Insuladd Insulating Additive mixed into house paint as finish coat. The outside of our house is 1312 sf, approx, not subtracting openings. So that's 5 buckets each, for a total materials cost of $1530.00.
All of that is supposed to reduce our AC-heat bill by up to 40%, which at an average monthly cost of $105, would be $504/year, and would pay for itself (materials only) in three years. It's also supposed to outlast ordinary housepaint, so I could wait until I build the addition and need to paint it, then paint the whole compoound.
Alternatively, I could drill holes in all my walls and have Icynene or BioBase foamed in between the studs, which would supposedly add R12 to the walls, at a cost of $2/sf (materials), or $2624.00. I don't remember how to figure the cost savings there. Perhaps a trip to the library to visit my old HVAC book is in order.
This is a very useful information for my husband who is going to re-paint our home this weekend. In doing so, he bought gallons of insulating and heat reflective paints from add4green because he is convinced that using such paints to re-paint our home’s roof, interiors and exteriors will help us save energy and reduce our heating and cooling cost. As a housewife who deals with budgeting my husband’s monthly income, I think any kind of saving is worth the trouble.
Posted by: Abbey Taylor | August 23, 2010 at 10:33 AM