BattWise is an independent site that works out insulation quantities, effective R-values and what an upgrade is actually worth in dollars a year.
It exists because insulation is sold in R-values but paid for in heat loss, and the two are related by a reciprocal that almost no buying guide bothers to show — which is why the first R-10 matters far more than the last.
Where the numbers come from
- IECC 2021 Table R402.1.3 for R-value targets by climate zone
- ASHRAE parallel-path method for effective assembly R-value
- heating degree days by IECC zone, and published fuel energy contents
Every page states the source and the assumptions behind its figures, because a number without its assumptions is not much use. Where a value is a code minimum rather than a measured performance figure, the page marks it as such.
Reciprocals, not R-values
Insulation savings follow the difference between two reciprocals, not two R-values. That single fact means the first R-10 of an upgrade is often worth eight times the last, and it is the reason "more R is always better" is bad advice.
What this site does not do
We do not perform Manual J load calculations. Our HVAC sizing pages are a sanity check on a contractor quote, not a substitute for the calculation many jurisdictions require on a permit.
Who runs it
One person, working on this around a full-time job. There is no editorial team. The thing that should earn your trust is that every R-value on the site names its climate zone and the code edition it comes from.
The heat-loss maths runs as code across every zone and assembly combination on the site, which is how a bad constant gets caught — it would be visibly wrong in dozens of places, not one. Mistakes get corrected and the correction is noted on the page.
How it is paid for
BattWise is free to read and funded by display advertising. No sponsored content, no affiliate links. No insulation manufacturer has any influence over what these pages say.
Getting in touch
Corrections and questions go to [email protected]. If you find an error, send it — see the editorial policy for what happens next.