[Strawbale] Forced air

[Rene Dalmeijer]

Mark, Don,

Rene
On Jan 8, 2008, at 15:49, strawbale-request at listserv.repp.org wrote:
>
> As far as the assertion that radiant heated houses have lower 
> thermostat
> settings, I had heard that frequently as well. So I hired a student in
> Nova Scotia to check a sample of each type of house: radiant flooring 
> and
> forced air. Here is the link to the results:
> http://www.cmhc-schl.gc.ca/odpub/pdf/62675.pdf
>
> Thermostat settings were the same for the forced air and radiant 
> flooring
> houses. The radiant heating industry didn't like the study. They said 
> it
> was not big enough, and that we did not measure comfort created in 
> those
> houses.

Don the knowledge Mark is referring too is most probably based on the 
research done by Fanger. I don't have it at hand at present but a 
higher radiant heat level of a surface is better able to compensate the 
effect of a cold draft or a cold surface like glasing then a higher air 
temperature. The theory behind the positive effect of radiant heating 
compared to higher air temperatures is that higher air temperatures 
sooner cause convection currents and stratification. Basically what 
Fanger found is that people experienced the same comfort level at a 
lower thermostat setting in a primarily radiant heated room then in a 
room primarily heated through a higher air temperatures. As you might 
know Fanger did very extensive research, with extensive data sets 
including control groups, into the perceived comfort level of occupants 
in buildings. The basic outcome of his research is that the difference 
is about 1-2 C in favour of radiant heating.

It would be interesting to see the same extensive testing done with the 
current crop of highly insulated houses with triple glasing etc. This 
could mean that air heating systems could be a good option for highly 
insulated buildings.The Passive house institute is promoting air 
heating systems in favour of other heat sources as these would be 
overkill seeing the insignificant amount of heat required for such 
houses. The forced air ventilation system is there anyway because an 
HRV is an essential part of the concept.