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Heat loss on DC rowhouse?

mandy_b Member Posts: 7
hi there,

I've been lurking for a while and reading Siggy's book in order to study up for a heating project I'd like to finish this summer. I am hoping to convert portions of the house to under-floor radiant but I want to make sure that I can get enough output to heat the house this way. So, I have to figure out my heat loss.

I live in a 105 year-old masonry rowhouse, attached on both sides, in DC. I have an old cast iron boiler that puts out 88 MBTU/h, and radiators that I've calculated to have an output of 56 MBTU/h. But I know that I can probably assume that both are oversized (certainly the boiler is if it's bigger than the radiators, right!?)

I've used some online tools to estimate heat loss, and I still plan to sit down with Siggy and map out every room in precise detail. But, one thing that has become clear is that my losses are probably dominated by air infiltration, because most of my house's perimeter is against my neighbors' houses, and I installed R38 in the attic a few years ago.

Does anyone on here deal much with row houses like mine, and know what rates of outside air infiltration is typical? My house has new windows, and my door weatherstripping is okay, but who knows how much air is seeping in through masonry cracks, etc!? I know I could do a blower door test, but I would expect this to overestimate my losses because some (most?) of the drafts, I assume, will come from my neighbors' conditioned spaces.

The best lead I have so far was on some diy site, where I read that the rule of thumb for *total* heat loss in a row house is 4 x living area x ceiling height. This puts me around 60k BTU/h, so, surprisingly near the radiators' output, but this rule seems way too simple to be correct. How can you possibly compute heat loss without considering windows and insulation? And, my radiators did keep the house warm enough when there was no insulation and drafty old windows, so I'm a bit skeptical that my current losses can be anywhere near the radiators' max output.

It would be great to hear back from any of you.


Mandy B.


  • Rich_49
    Rich_49 Member Posts: 2,766
    Posted in Main

    RadiantMandy ,

                   Sounds as if you have plenty of muscle to handle the entire load at design .   A room by room analysis is certainly in order and many here can assist with that .

       Would it be possible to post dimensional drawings of the home including room dimensions , lengths and heights of exposed walls and their R values , size of each window and door and their construction , ceiling height , what type of finish floors there are and will be  (even in the rooms not to receive radiant ) , your desired indoor temp at outdoor design and please include the radiator characteristics in each room ? 

      Rules of thumb more often than not become rules of bad design . Could you also include what make / model boiler you have and possibly date of manufacture ?  It is hard to imagine that any of the rooms may not be able to utilize radiant floor but it does happen and when it does we often look to the ceilings or walls as emitters .

      We will be waiting 

    You didn't get what you didn't pay for and it will never be what you thought it would .
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