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# Heat loss on DC rowhouse?

Member Posts: 7
(originally posted in radiant forum but main seems more appropriate. sorry! im new here)

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.

Thanks!

Mandy B.

• Member Posts: 7
data

Total cubic footage: 14.5k

Design temp: 14F

Exterior walls: one @ 15'w x 25' h, one @ 26' x 28' (house is L-shaped)
• Member Posts: 2,766

Mandy ,

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 .
Langans Plumbing & Heating LLC
732-751-1560
Serving most of New Jersey, Eastern Pa .
Consultation, Design & Installation anywhere
Rich McGrath 732-581-3833
• Member Posts: 2,766

Mandy ,

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 .
Langans Plumbing & Heating LLC
732-751-1560
Serving most of New Jersey, Eastern Pa .
Consultation, Design & Installation anywhere
Rich McGrath 732-581-3833
• Member Posts: 3,656

Siggy's software will allow you to compare room heat loss with radiant output for each room. The new radiant zone would have an increased output if installed on top of the floor (Climate Panel or QuickTrak) but for whatever method is used, the rooms need to be analyzed with the correct software to make sure supplemental heating is not required. Is the home air conditioned?

You may want to talk with Dan Foley of Foley Mechanical. He's done many a DC rowhouse and is one of the best hydronic (and HVAC) experts you can find.

I'd be considering changing the old cast iron boiler to a condensing mod-con and adding an indirect storage tank for DHW. You're going to have to repipe the "near-boiler" piping anyway and it's a good time to go for greater efficiency, if budget allows.
• Member Posts: 7
room-by-room

hi Rich,

thanks so much. Like I said, I'm planning to do the detailed room-by-room analysis, but I never expected that the people on here would be willing to help with that level of detail! I hope to get around to this in the next couple of days, I'll post when I've got all the details together.

Thanks,

Mandy
• Member Posts: 16,827
One question that hasn't been asked

is your current system a steam or hot-water system?
All Steamed Up, Inc.
Towson, MD, USA
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting
• Member Posts: 7
same ballpark

Thanks for your estimates, bc3510! In my calculations I had been budgeting for between 1 and 2 total air changes per hour. It looks like your estimate lands a little bit below that. I guess I hadn't thought to just multiply that by the fraction that is outside-facing, but that makes perfect sense!

I guess I asked this question in part because my total-house estimates still had me at well below my radiator output on design day (usually around 30 MBTU/h), and infiltration is the dominant part of that, and so I wanted to make sure I wasn't way off. I'd have been worried if you came up with 30 MBTU/h for infiltration alone, for example, but it sounds like that would be well above your estimates as well.

Mandy
• Member Posts: 1,850
System

As well, be it steam or hot water and if you don't plan on doing it yourself I agree with Paul, call Foley Mechanical. You would be hard pressed to find a more competent or conscientious contractor. He may not be the low bidder, but you will get your moneys worth. A good contractor will do the heat loss himself and discuss options and your needs. He will not oversize it to cover his butt because he doesn't need to.

JMHO,

Rob
• Member Posts: 7
joist trak

hi Paul,

I have been planning on doing Joist Trak. Under the tile floors in the kitchen, I expect to get about 5000 BTU/h out of the radiant, but this room has the largest outside exposure (50% of wall area is outside-facing). I have also been considering doing the Joist Trak in the remaining portion of the first floor, though that would be under wood floors so the output per sq foot is considerably lower (but then again, these rooms are mostly not outside-facing). Clearly a room-by-room analysis is needed, I just haven't gotten around to it yet, especially since I have yet to nail down the infiltration component of the heat loss.

Oh, and yes, the home is air conditioned.

Thanks for recommending Dan Foley. I've seen his name pop up in a number of places, but I wasn't sure whether he just sticks to bigger projects (his website seems to emphasize multi-unit residences, commercial buildings, and high-end single-unit residences). Perhaps I'll give him a call once I've got a clearer picture of what I'm facing, although I am leaning at the moment to DIY these upgrades.

I agree that the mod/con upgrade would be nice, but my current boiler is not *so* oversized as to make the likely savings worth it. I calculated that I would save about \$500 a year in energy costs at my previous usage, but that was when I could feel the wind blowing through my drafty old windows. I expect the savings to be even less now, and my old Crown Aruba is running strong, so I'll probably opt to save the money for other home improvements.

Mandy
• Member Posts: 7
hot water

it's hot water.
• Member Posts: 2,479
I live in MD and

Have worked on DC row houses a lot. . Since there are two walls that have no heat loss on either side the boiler does not have to be very big. I usually put in a 60,000 btu modulating condensing boiler and it has plenty of capacity. Any good contractor has heat load software and can do a heat load plenty easy. Dan Foley is one of the best down in Springfield. If you stay with the cast iron boiler you will have to be careful to protect it from the cool water return coming from the radiant floor as it will hurt the cast iron boiler by causing condensation that it is not designed to handle. The near boiler piping will have to be modified to obtain that protection.
• Member Posts: 2,766
Infiltration

will be speculation at best unless you have a blower door performed where they take the space to -50 pascales to determine how much air can be pulled through the envelope .  Heat loss programs get close after entering all the information but depend a lot on whether all the components were installed really well , not too often , that's why they have the fudge factors built in .  Many utility companies offer this service as part of an energy efficiency program  , you could check that out but be very wary of the fine print .

Will you be putting in new flooring ?  If so I would recommend an above floor product , they are more responsive and will lower your SWTs .  As far as on top of sub floor products I recommend Sun Board panels , they really perform well and at 8" on center are probably the best value and heat more evenly than other similar products due to the graphite coating . I use everything Uponor for the most part but have to say when I need a pre manufactured panel I do not use quik trak because the head losses usually do not allow me to use ECM circulacirculators that I prefer in my designs .  If you are certainly going under the sub floor the Uponor Joist Trak is comparable to others and will do what you need it to .

The recommendation to contact Dan at FMI is one of the most intelligent pieces of advice I have heard on this site lately .
You didn't get what you didn't pay for and it will never be what you thought it would .
Langans Plumbing & Heating LLC
732-751-1560
Serving most of New Jersey, Eastern Pa .
Consultation, Design & Installation anywhere
Rich McGrath 732-581-3833