I'll address these questions in order and try to elaborate a little later. To start off, this project would be once piece of a much larger renovation project which will entail adding two new bedrooms to the home and turning one existing bedroom into a bathroom for a total of three bedrooms and two full baths:
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Originally Posted by HVACDave
So what's the plan as far as the system goes? Do you want to control each rad separately or run the house as a single zone?
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It would probably help to show just what I'm trying to heat, so here is a drawing which shows the envelope of the existing home (in blue), the proposed addition (in pink), and the part of the house that will be reworked to create a hallway and a bathroom from an old bedroom (in grey). All told, including the 400 SF or so of finished space in the basement it's about 1300 SF. In terms of the finished space, I would think that it could all be run on one zone (I can't see a reason for wanting to shut off any of the rooms really), but I've also thought about heating the garage (right now its unconditioned space), so that could be a separate zone. Basically, two zones maximum, unless I'm missing something. Here is the drawing:
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Originally Posted by HVACDave
What type of fuel are you planning for the boiler? (oil, electric, outdoor wood unit?) You can use pex for hydronics, as long as it is rated for hot water heating.
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Basically I'm planning on installing two boilers, an oil boiler to serve as a backup/source of heat for extended absences (more than two days), and a wood gasification boiler which will serve as the primary source of heat. I will also be incorporating pressurized storage, hopefully about 1000 gallons in the form of four 250 gallon decommissioned propane tanks. Here is a diagram laying out the system:
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Originally Posted by HVACDave
What area of the country do you live in? Is A/C a concern?
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We live in the Northeast (NJ) so A/C is definitely a concern which will Right now we have A/C through the existing ductwork for the oil furnace. I plan on moving the air handler to the attic and running all new insulated duct with registers in the ceiling. The already insulated duct, air handler, etc...will then be buried in a blanket of cellulose (with attention given to proper clearances and sealing procedures of course) for an R-60 rating. Luckily I have a friend in the HVAC business who is willing to help advise on this part of the project-he only does forced air work though, which is why I'm still searching for answers on the boiler project. In addition to the R-60 attic, at the time of the renovation we'll also be tearing off the old vinyl siding on the existing home and doing major air sealing from the outside with foam, housewrap, tape, etc... Once that is accomplished the entire house will be sheathed in two layers of 2" rigid foam with staggered seams (all taped) secured with 1x3 battens. Finally the entire house will be clad in Hardi-Plank siding. I took this idea from Building Science:
Residential Exterior Wall Superinsulation Retrofit Details and Analysis
This will give me an R-30 wall. I did a heat loss calculation based on these numbers and came up with a recommendation of an 80K BTU boiler. Please let me know what you think of that number. If its good I would be inclined to go with a low end (in terms of efficiency since it won't be used much) 80K BTU oil boiler, and a 100K BTU wood boiler. The current budget wouldn't likely allow it, but I'd like to the leave the possibility of adding solar collectors in the future. The rear of home faces directly south and we have no tree cover (which is part of the reason A/C performance leaves something to be desired), so I would likely be able to supply all of my DHW needs from about May to September with the solar. I am eager to hear a professional critique of these ideas. Any recommended reading you can think of for a project like this?
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