How to Calculate BTUs for Radiant Heating Heat Loss in an Oregon Home

Calculating heat loss in terms of BTUs is something best left to the professionals but can be done on an estimation basis if you’re considering initial options for your home. As you might expect, the higher quality of the insulation and windows, the less opportunity for heat loss.

One of the most common errors made in estimating your radiant heat need on your own is looking at your total potential heat loss in the space that you’re looking to warm. Heat loss is obviously critical to the overall effectiveness of your system. It should be estimated as accurately as possible (just another reason it’s best to let a professional radiant heat team install and calibrate your system).

What is the Average Output of Radiant Heat Flooring?

The general estimation is that radiant heat flooring warms at 25 BTUs per square foot. However, windows, doors, insulation, and broad temperature shifts of your specific environment can sway this number. Older and lesser-insulated homes can have more small gaps and nooks that let heat escape.

When looking at a radiant heat system, you should enlist the help of a trusted radiant heat expert to ensure that you’re not oversizing for your particular space. A heating system that’s too large for the designated space equals inefficiency and more operating costs. It can also contribute to unnecessary temperature swings easily avoidable with an appropriate install the first time.

Can I Calculate Radiant Heat Loss & Difference On My Own?

Typically, you’re going to want a professional to calculate heat loss, but you could use this general guide:

  • No insulation in the space with loose-fitting windows: 60-100 BTUs / Sq. Ft.
  • R-11 insulation in walls and ceilings, limited crawl space insulation with tight-fitting windows: 50-60 BTUs / Sq. Ft.
  • R-19 in walls, R-30 in ceilings, R-11 in floors in tandem with tight windows: 30-35 BTUs / Sq. Ft.
  • “Energy Star” rating with R-24+ insulation, R-40 in ceiling, R-19 in floor, and highest quality window sealing: 20-25 BTUs / Sq. Ft.

Of course, in a region like the Pacific Northwest, the temperature can shift dramatically, even over a short time, leading to significantly different numbers from these guides.


If you’re considering a radiant heat flooring installation in Portland, it’s best left to the pros. Hiring a qualified radiant heat supplier like The Earth Heating means you’re putting your home’s heating needs in good hands. They’ve been a trusted source in the Portland metro area for a decade. Call (503) 788-7777 to learn more and schedule a free consultation.

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