Radiant Heat Information

In the first post of this series, I hope I’ve convinced you that sizing matters.

In this section I’ll explain further why a detailed analysis is just as important.

A common practice in the industry is to use a “rule-of-thumb” estimate of so many watts or BTUs per square foot. (This number may vary from region to region, due to local climate conditions.) Really, that’s nowhere good enough or appropriate for your home. Your home isn’t “average” – it’s going to have unique features and design to meet your needs and lifestyle and no “rule-of-thumb” estimate is going to be able to reflect that. Your choices of insulation levels, windows sizes and types, etc. all affect the heat loss of the rooms on a room-by-room basis. A properly sized system will reflect those decisions.

At best, a “rule-of-thumb” can provide a very rough estimate of what size of heating system you’ll need for the home (assuming that the rule is anywhere near being accurate), but it will not tell you how that capacity is best distributed in the home. All too often the “rule-of-thumb” is applied equally across every room. And that practice is just plain stupid.

For that, a graphical example is in order:

Sample Floor Plan

Take note of the Dining Room and the Kitchen in this example. If we were to apply the same “watts per square foot” rule we’d go horribly wrong. Notice that the Kitchen has a single cold wall and no windows. Compare that against the Dining Room that has a lot of windows, an exterior door (probably glass, too) and three outside walls. On a square foot basis, the Dining Room will have a much higher heat loss per square foot due to these factors. If we sized the heating system according to the “rule”, we’d have too much heat in the Kitchen and certainly not enough heat in the Dining Room. Think about that for a second if you will – you’ve chosen a design that gives you plenty of natural light with a nice view so that you, your family and guests can have an enjoyable dining experience. But your expectations will be dashed due to your being uncomfortable in that space!

Let’s take another example. Bedroom 2 and Bedroom 3 are roughly the same size with the same amount of windows. However, Bedroom 2 has proportionally more exterior wall space – and it’s the exposure to the exterior that dictates how much heat loss you will have. Yes, you’ve got it – Bedroom 2 will need more heating capacity than will Bedroom 3 and your heating system needs to be able to reflect that.

Shameless Plug: SmartRooms is designed specifically to be able to address this requirement. Our systems can easily handle this kind of granularity. Doing so ensures your comfort while being cost effective and energy efficient.