Home Energy Heat Loss Information, Simulation Software, and Energy Audit


Estimating home heat loss, including R values of materials, infiltration loses, and the thermal performance of real walls.


Simulation software to estimate the thermal performance of a passive solar or conventional home. 


Estimating Solar Fraction for active solar heating systems.

The Home Energy Audit calculators that help you to find changes you can make to save energy.


Directory of this page:

Home Heat Loss/Gain and Passive Solar Home Design Software



This is very easy to use, yet very capable simulation software for estimating the energy/thermal performance of a passive solar or conventional home.  Weather files for over 700 worldwide locations. While it initially appears almost too simple, by using the "advanced tab" it can handle a wide variety of situations.  It uses a one hour simulation time step, and weather files that cover a full year of typical weather.  It has been carefully validated. 

It is limited to 1 zone, and does not handle sunspaces.  It is a free download.

For people outside of California: Here is how to get and use a weather file for your area with HEED.

How Much Collector Area Do I Need To Heat My House?

Or, Estimating Solar Heating Fraction

Estimating Solar Fraction for an array of collectors...

A simpler example on using Andy's simulation: using the simulation to estimate energy, fuel, and CO2 savings for a collector array...

This is a question I get asked a lot.  Its a tough question that depends on many things, but here is a method that you can use to get a pretty good idea what your solar faction is likely to be for your collector array...

Its fairly lengthy to use, but not difficult.



For precompiled Resfen data on many window types for many locations, use the "Window Selection" tool here:



Resfen allows detailed analysis of window choices for a wide variety of windows.  It is a full hourly simulation, and offers weather files for many locations.  Easy to use.





ENERGY-10 is a PC-based design tool that helps building designers quickly identify the most cost-effective, energy-saving measures for small commercial and residential buildings.  It supports rapid comparisons of energy saving strategies.  Limited to 2 zones.

Cost is $300, or $60 for students -- just think how much energy would be saved if this program was made free!

Calculators: Passive solar heating, overhangs, thermal mass, heat loss, radiant heating...

Borst Engineering and Construction provides a number of calculators that are helpful for solar heating, and renewable energy applications.

They are a small engineering consulting and analysis business -- "We are do-it-yourselfers (DIY) at heart and we support like-minded people"

Simple Home Heat Loss Calculators
These simple calculators are not simulations and will give less exact numbers than the ones listed above, but you may find them easier  and quicker to use, and they do give reasonably accurate estimates of heat loss.
Insulation Upgrade Cost Saving Calculator



Calculate how much money and greenhouse gas you would save with various insulation,  window, or window treatment  upgrades.

Very easy to use.

Home Heat Loss Calculator



This is a simple home heat loss calculator.  It provides rough estimates of design heat loss (for furnace sizing), yearly heat loss, greenhouse gas emissions, and estimated yearly fuel bills.
Thermal Performance of Walls -- Including Walls with Thermal Mass
Whole Wall Heat Loss Calculator

Oak Ridge National Laboratory


Home Energy Magazine Article



An online calculator to estimate the R value of entire walls, including the areas where R value is reduced by corners, window frames, door frames etc.

Works for a wide variety of wall constructions.

Results based on testing of actual wall sections.

Thermal Mass - Energy Savings Potential in Residential Buildings

ORNL Paper



ORNL study of the benefits of incorporating thermal mass in walls, and comparing different layerings of thermal mass and insulation.
R Values of Materials
R values for typical Building Materials



Table of R values for typical insulators and building materials.
Infiltration Heat Loss
Infiltration Heat Loss



Estimating the saving for reducing infiltration heat loss.
Moisture Sources in the Home
Home Moisture Sources Common sources of moisture in the home with amounts of moisture for each.
Home Energy Audit
An Interactive Tool for Saving Energy at Home

Interactive Home Energy Saving Tool


A cute new tool from Energy Star that identifies energy saving tips on a room by room basis.
You can give to your kids, and let them nag you into making some energy saving changes to make the planet better for them.
Energy Savers from DOE EERE site


Energy Tips from EERE (2.7MB pdf)

"Energy Savers" for home owners (insulation, appliances, lighting, ...) energy saving advice.

The Energy Tips 36 page booklet is good.

Energy Star Home Energy Yardstick



A helpful and easy to use Energy Star calculator you can use to see how your homes energy efficiency compares to others in your area.
Home Energy Saver Audit/Calculator



A Do-It-Yourself home energy audit

Fill in details on your home location, size, construction, etc.  The calculator estimates your current energy use, makes recommendations on changes and estimates the cost saving and pollution benefits.