Your building loses heat in winter and soaks up heat in summer, through the roof, the walls, the floor, the windows, and every gap. This app figures out how much of that is happening right now, and turns it into a simple list: if you had one more dollar and one more hour, where should they go?
That's the whole job. Not "insulation is good," but which square foot of this building, in your weather, pays you back the fastest.
A few reasons people find it useful:
Spending money in the right order. Every dollar you spend on this building can go to a lot of different places. This app sorts them so the best ones come first, and tells you when a fix is worth it and when it isn't yet.
Picking your start date. If you'll be living or working in the space while you build it, starting in the wrong month can mean weeks of misery you didn't need. This app shows you what the building is doing to you in any month you pick, before you commit to a schedule.
Building somewhere new to you. If you've never built in this climate before, your gut instincts from somewhere else might be wrong. This app plugs in the real sun and the real weather for the actual spot on the map.
Handing this off to someone else. If you're building this for another person, you can just give them this chart. It explains itself, and it's a fair, honest way to show what you found and why you're recommending what you're recommending.
Everything below this is how the app actually does its math, if you want to know.
Your equipment's delivered output divided by the building's load right now. Under 1.0 the machines lose and the room drifts to the temperature shown beside it. Above 1.5 you have margin. Far above it, the compressor cannot modulate that low and starts cycling, which is its own kind of failure.
A single-hose portable exhausts room air it already paid to cool and pulls hot outside air in to replace it, so it delivers around 58% of its sticker. A heat pump loses roughly a third of its output at 25°F. The nameplate is struck through and the honest number sits under it.
Drag it. The building turns with your finger and every number follows. Rotating the same building through a full circle moves the load by more than ten percent, for free, and orientation is the last thing you can still change before the trucks arrive.
The dial is a sky chart. The rim is the horizon and the inner ring is straight overhead, so the amber curve is the sun's actual path across your chosen day, from its sunrise dot to its sunset dot. The dashed line runs clear across the dial: sun on one side, shadow on the other.
Real, not decorative. Its length is your ridge height divided by the tangent of the sun's altitude, cast on the bearing opposite the sun. Scrub the hour and watch it swing. Scrub the month and watch it grow. That grey shape is where a tree, a fence, an RV, or a condenser would stand in the shade, and where they would not.
Every wall and every roof plane gets its own angle of incidence, its own irradiance, and its own sol-air temperature, which is what a surface actually reaches once it has absorbed sunlight. The walls on the dial glow warmer as they heat.
Outdoor air is not what your wall feels. A dark surface in full sun runs sixty degrees above ambient, a white one about twelve. Absorptance is worth more than most insulation and costs a bucket of paint.
Height is the whole mechanism. A barrier of height H standing D feet off a wall shades it up to H minus D times the tangent of the sun's altitude. A five foot shrub covers half your wall at sunset and none of it at noon. A solid fence three feet off a wall shades nothing at noon while still killing the airflow behind it, and at that hour it makes the wall hotter. Deciduous leaves pass thirty percent of the summer sun and eighty five percent of the winter sun. Evergreens pass fifteen percent of both, which is why an evergreen on your sunny wall is the most expensive thing you can plant.
The bar splits the total into the assemblies producing it. In heating, a sunlit south window can go negative, shown in green, because the sun is heating you for free.
Each row is one step up a ladder, priced three ways: heat removed, money, and hours of your labor. It recomputes after every change, because insulating the roof changes what the walls are worth. A cheap improvement on a terrible assembly is enormous. The same improvement on a good one is nothing. Do them in the order shown, not the order that feels good.
It evaluates a single instant and has no thermal mass, so it will never show you two in the morning. That is the one hour on which masonry, adobe, and rammed-earth should be judged, and this chart will keep making them look reasonable at three in the afternoon. It assumes a clear sky and a light wind, and it puts peak conditions on every surface at once, which never happens, so it runs pessimistic. Trust the ranking. Test the numbers.
Materials at 2026 prices for someone doing the work themselves. They are estimates. Your lumber yard is the authority, not this app.
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