# Optimizing a heating system

I am seeking software I can use to better understand the thermal properties of my house. The main two consumptions of the house are water and heating. I'm interested in optimizing the heating.

Eventual goal would be each room has a motion detector, thermometer, and heat source, and good user interface. Walls are well insulated, doors seal tight, etc. But first I need to measure it, so I know where to begin.

Given some subset of internal and external temperatures, times when heat is on or off, location of furnace and vents, square feet of window, wall, and roof, insulation type, etc. there ought to be a good picture of what is going on. What tools exist to work with this?

I'd like to analyze a range of questions such as:

• What will be the quantitative benefit of foam-filling my walls?

• which doors to leave open/closed to minimize heat to unused rooms?

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## 1 Answer

It sounds like what you want is a set of heat loss calculations. These are the calculations a heating contractor would do in order to determine how much power (BTU output) a furnace/boiler would need in order to keep your house warm. A heating system is then sized such that it can overcome the heat loss your home would experience on the coldest day of the year.

These calculations are based on the area of each room, exterior walls, number of windows and doors, type of insulation, etc. I saw an episode of Ask This Old House that included a heat-loss analysis using software that calculated this using a house model / floor plan entered by the contractor. According to this show page (http://www.thisoldhouse.com/toh/tv/ask-toh/products-and-services/episode/0,,20321333_20311273,00.html), that software was made by WrightSoft.

Unfortunately, this software seems to be aimed at contractors rather than homeowners, and has a price tag of \$200-\$500. It is also probably rather technical. There are some other options, including some free online heat loss calculators. But why bother, when you can probably have a heating or insulation contractor come to your house and do these calculations for you?

In Massachusetts, where I live, the utility companies offer an energy audit service where, among other things, they inspect and measure your house and offer you various options for adding insulation. For each option, e.g. blowing cellulose insulation into the exterior walls, they also list the estimated savings per year, based on local energy prices. Using that, you can calculate how many years it'll be before the insulation work pays for itself. In my case, about \$2000 of insulation work would pay off in between 2 and 3 years.

If utility companies in your state don't offer this service, you may still be able to find an insulation contractor who can. And for figuring out which doors to close to reduce heat to unused rooms, why not do some experiments? You can buy a thermometer with multiple remote sensors, and watch how the temperature fluctuates in your unused rooms.

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Also, in Massachusetts the government may pay for up to 75% of your cost (up to \$2000) to add insulation and make other energy-efficiency improvements. See masssave.com. Other states may have similar subsidies. – Vebjorn Ljosa Dec 15 '10 at 15:14