Overview
Manual J load calculations are only as good as the assumptions behind them. This is the old garbage in = garbage out problem for any model.
But manually editing assumptions—like insulation levels, window type (clear glass vs. lowE), or infiltration rates—can be time-consuming, so we created our smart starting assumptions feature.
Important Note:
Even with intelligent starting defaults, it’s still critical to verify construction details in the home.
The smart starting assumptions are set automatically based on:
Year built
Location (climate zone)
Both are set automatically once you enter the project address. If you are not connected to the internet or want to modify the year built to match the most recent major renovation, you can manually change it in Building Profile -> General -> Year Built.
You still need to verify what is going on in the home
Even with smarter defaults, it’s still critical to verify construction details in the home.
For example, a home built in 1950 may have had its windows replaced (two or even three times) or undergone attic and wall weatherization. Our model makes educated guesses based on sampled data, but it’s not perfect — especially at the individual home level, where site-specific details will always outperform probabilistic assumptions.
How does smart starting assumptions work?
We built our model using 1,000,000+ samples of real homes in the U.S. via data from ResStock and EIA RECS data. By combining these sources, we created a lookup system that aligns expected construction details with climate zone and vintage for single-family homes across the U.S. in 10-year increments from pre-1950s to 2020+
The model adjusts assumptions for:
Wall and ceiling insulation R-values
Window U-value and SHGC
Air infiltration (Manual J "tightness")
Based on:
Year built (or last major renovation)
Location
This methodology incorporates:
Typical building codes and construction practices by vintage
Regional differences in construction standards and energy retrofit adoption
The likelihood of energy improvements based on geography, policy, and home age
All of this is handled automatically after you create a new Amply project and enter an address.
Renovated Historic Home?
Have a home that was built in 1835 but was gut-renovated in 2015? No problem, just modify the "year built" to 2015 and we will update the starting assumptions for that vintage in the project's location.