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retrobolted
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Posts:14
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| 04/15/2009 4:01 PM |
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Hi All,
I'm building a small (850 square foot) house in Ontario. It's stick frame, but reasonably well insulated. One story (with lofted mezzanine), slab on grade construction. Quite a bit of (high quality) windows. I have been having a difficult time deciding on a fuel source for the infloor system and am hoping to get some help from the very knowledgeable people on this forum. I have received a few quotes from local heating/plumbing people, but their recommendations worry me based on what I have read on this forum.
Here's the problem: The house is small, so that even with big windows I anticipate a low heating demand (heat loss calcs are being done as I speak, but I don't have the figures yet). The house is also 100% off-grid, which means there are serious constraints in terms of electrical consumption for the heater (e.g., I think power vented appliances are out). There are also pretty strong space constraints -- the house doesn't have a big utility room, as a normal house does, and moreover, no part of the house where a heater/boiler could go is attached to an outside wall, which means all venting has to be through the roof.
The local contractors all were recommending very powerful mod/con set ups, fired by propane, with an indirect water heater. I was attracted to this because of the potential efficiencies, given the price of propane in this area ($2.70 a gallon). But the upfront costs worried me a bit, but more importantly from what I
have read this kind of set up would be a mistake, given the small house
size and anticipated low-ish load. (The house will also be single occupancy, with no dishwasher, so DHW demand will be quite low too.)
For a while I was considering putting an oil burner in the detached garage (or, more precisely, in a separate utility room in the detached garage), and running the lines underground to the house for the radiant, and using a propane tankless heater inside for DHW. This would free up some space in the interior for another closet, and I think oil is a fair bit cheaper than propane here. But I am a bit turned off of this idea because I have to have propane for heating and it seems dumb to have both a propane tank buried in the yard and a oil tank hiding behind the garage.
At the moment I am leaning toward a Bradford White Combi1 or Combi2, with atmospheric vent. My thought is that I could get both the domestic hot water and space heating in one unit the size of a hot water tank, which would meet the space constraints. It doesn't have a super high efficiency rating, but it noticeably better than a normal water heater, and might compete okay with a pricey mod/con that is running at low capacity. Does anyone have any thoughts on this setup? If there is some other solution I should consider, I would be extremely grateful for the tip. (I should say that I have scoured these forums at length and not found something that addresses my particular situation.)
One issue that worries me: is an atmospheric vent water heater noisy at all? I ask because it will be largely within the normal living space of the house. If it is, I would have to go with a mod/con or with a heater in the garage.
sorry for the long post -- I have been wracking my brains for ages trying to figure out a solution given the constraints.
thanks,
retrobolted.
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BadgerBoilerMN
Registered Users
Basic Member
Posts:311
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| 04/15/2009 6:51 PM |
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I like the Combi 1, I do not use the combi 2 as it is double-wall and has no place in domestic (residential) applications, existing entirely by the efforts of self-serving lobbyists (factory reps) and adding unnecessary cost up front and in operation. Atmospheric water heaters are very quiet and though you will have to have combustion air, if the room is airtight to the living space you will have an excellent setup.
I have designed many solid fuel boiler systems with Combi-1 back up and many smaller home, such as yours with the Combi standing alone.
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MA
www.badgerboilerservice.com |
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retrobolted
Registered Users
New Member
Posts:14
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| 04/16/2009 4:21 AM |
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Thanks Morgan -- that is very helpful. I know in the past you have recommended the Combi heater, which gave me some confidence in using it.
You mentioned a set up in which the heater was in a sealed room with fresh air intakes for combustion air. We could do this, assuming the fresh air intake lines could run vertically (which I think they could, from the Combi1's product literature). Could I ask however why you are recommending this rather than having it draw combustion air from the living space of the house? I had thought we could put the heater in a 'closet', so to speak, with substantial openings for fresh air intake. Did you recommend the other option because of noise (having a sealed room would make the unit quieter) or for some other reason (e.g., safety)? I am hoping we can avoid the specially ducted sealed-room option because the fresh air intakes (two required per Combi1 literature) would be a major perforation of the building envelope (in what is a very cold weather environment).
By the way, the heat loss calcs came back at 19,000 BTU. The actual figure will be a bit higher because he had assumed 3 insulated steel doors rather than the 3 glass doors spec'd on the drawings, but that gives a rough indication of expected heat loss (degree days about 7500 F).
thanks again!
retrobolted.
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BadgerBoilerMN
Registered Users
Basic Member
Posts:311
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| 04/16/2009 4:26 PM |
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You should have an experienced designer review all advice gathered on the Internet. Your life may depend on it!
To that end; all fossil fuel breath oxygen and exhaust water vapor, CO2 and NOx and various other gases and chemicals. If your gas-fired appliance does not get enough oxygen it will produce CO, which can kill you or worse.
So you will need outside air (there is an excepted formula for this) and I would isolate the mechanical room from the rest of the house. I would not forget to install an HRV, as this is an indispensable appliance for any new construction, more so for super-tight SIP or ICF homes.
If you want a tight envelope then all penetrations will be through the slab and through the sidewall. We are back to a sealed combustion ModCon. They modulate down to 15mbtu/h.
You know how I am about Mod/Cons and indirects. I design most of my systems with this technology. No worries about combustion air, and only one or two holes through the envelope.
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MA
www.badgerboilerservice.com |
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retrobolted
Registered Users
New Member
Posts:14
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| 04/22/2009 5:45 PM |
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Thanks Morgan. I appreciate the information. We have decided against having a natural draft appliance in the house, on your advice. Direct vent isn't an option given the design, and power vent would consume too much electricity, given that we are 100% off-grid. What we have decided to do is locate the utility room in the nearby detached garage, where a direct vent appliance can be housed. We'll bring the water to the house with a very well-insulated pipe. This has the added advantage that the little bit of heat lost through the wall of the HWH will keep the wel-insulated utility room, which also houses the off-grid batteries, well above freezing, which is good for them.
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gregj
Registered Users
Basic Member
Posts:218
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| 05/01/2009 11:42 AM |
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Don't the batteries have the potential to give off hydrogen? Aren't they suppose to be away from flames? You'll lose btus from the underground piping.
I don't think Morgan meant you have to remove the mechanical room from the house when he said to isolate the mechanical room. You just need to isolate it within the house so that it has it's own adequate fresh air supply and does not exchange air with the rest of the house. |
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BadgerBoilerMN
Registered Users
Basic Member
Posts:311
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| 05/01/2009 11:54 AM |
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Thanks Greg;
You are right. This, like so many, is a job best left to professionals. I often forget to whom I am speaking and assume it is a fellow contractor.
This type of design work takes my full attention and I apologize for my error. One should take "free" advice from the various blogs with a grain of salt. As this case proves, it is easy to misunderstand the premise and come to the wrong (possibly fatal) conclusion.
All DIY radiant floor, boiler, water heater, solar, wood boiler, off-grid, mechanical systems should be reviewed and inspected by a paid professional.
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MA
www.badgerboilerservice.com |
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HarryZ
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New Member
Posts:5
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| 10/30/2009 7:35 PM |
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BadgerBoilerN,
Just scanned through this post, does the Combi1 cost a lot, say >$2,000? Seems you've got a lot experience with it. Can you provide a ballpark number (by +/-$500)?
Thanks in advance.
Harry in Michigan |
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BadgerBoilerMN
Registered Users
Basic Member
Posts:311
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| 10/30/2009 8:12 PM |
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| Depends on where you live, generally more than $2000.00. |
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MA
www.badgerboilerservice.com |
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