[Strawbale] Forced air

[Mark BP / Low Energy Design Ltd]

Rene Dalmeijer wrote:

>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 certainly had Fanger's PMV index in the back of my head, but I know 
little about his research methodology, or the extent to which he 
directly compared different heating delivery types.  The only research I 
was directly aware of was a series of student projects (about 1984; 
probably unpublished) at the University of Durham which the professor 
responsible asked me to review, and which demonstrated that 
stratification was indeed minimal for the underfloor radiant 
installation considered, and that lower comfort temperatures than 
expected were possible in that building.
Thanks for this Rene - gives me a useful direction to look for more 
substantial research on the subject.
M



> 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.
>
>
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