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Manual J question

it's up to you to decide how many people ought to be in a room in "full" conditions. IIRC, they assume a 400BTU/person load, which is on the low side, i.e. resting. I assumed 2 people per bedroom.

One area of caution I would think are "public" spaces that are also used in "private" conditions. With a well-insulated house, ample people capacity in a room, and a 600-800BTU/person load, you can end up with very lopsided load/capacity conditions, i.e. way too much capacity when only 2 people as opoosed to 20 people are using the space. That could lead to short cycling, clammy conditions, etc. unless you can stage the output.

In most homes, the additional load that is represented by people is quite is usually small and pales in comparison to the loads posed by insolation via the windows, for example. For example, 10 people at rest add 1/10 the heat to my house that the sun does via the windows on a design day. Thus, I'd like to think that while accounting for people and appliances is certainly the right approach, in most homes the resultant deltas are not that high.

If this is a home that is designed to host large crowds, the design conditions become a lot trickier. For example, how does one account for exterior doors being left open in the summertime, as many people do when they host parties?


  • Rodney Summers
    Rodney Summers Member Posts: 748
    Manual J question

    When determining heat gain from Manual J calculations, is there a rule for how many people to put into a residence and where? SpacePak, a manufacturer of high-velocity air handlers, told me that their rule is to count two persons for a master bedroom plus one for each additional bedroom and to then place this total body count on the main floor or, in any event, in the areas of the home most commonly used. Is this consistent with Manual J instructions?
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