Major remodeling project in the next few years-Boiler for small, tight, well insulated house?

[Badfish740]

With the housing market being what it is my wife and I have decided that it is likely in our best interest to stay in the home we purchased in 2008 until we retire. We had thought of moving for more property and to be "out in the woods" as well as to a larger home, but expanding what we have will make a lot more financial sense. The plan is basically to add a master suite by converting our existing attached garage to living space (I get a 25 x 30 pole barn out back as compensation ). At the same time I want to reside the house, seal it up well, add a considerable amount of insulation in the form of foam board (see here: (broken link removed to http://www.buildingscience.com/documents/information-sheets/high-r-value-wall-assemblies/high-r-wall-12-exterior-insulation-finish-systems-eifs-wall-construction?topic=doctypes/enclosures-that-work/etw-high-r-value-enclosure-assemblie) ), and finally seal up the attic and apply blown cellulose. The goal will be a very tight, well insulated, simple box (basically a 24 x 50 rectangle). Total square footage after the conversion will come in at just a hair over 1200SF, so it will still be a fairly small house.

Right now we have forced air oil heat supplemented by the Englander furnace, but we want hydronic for a lot of reasons. The Englander is great and keeps us warm, but we hate the dust and dryness that is inevitable with forced air heat in the winter time. Also, the heat is very uneven due to a poorly designed distribution system which creates even bigger problems in the summer as the AC is barely adequate. What I'd like to do is install a hydronic system from scratch using wall panel radiators in each room. The air handler for the AC would be moved to the attic and a new dedicated ductwork system would be installed there with registers in the ceilings. The AC ductwork would be sealed and wrapped in insulation and then buried in the cellulose for maximum efficiency.

I did a heat loss calc (Using Built It Solar's calculator) assuming good tight air sealing, R-20 walls, and an R-50 ceiling, and came up with a design heat loss of 22,339 BTU/hr. As I understand it in terms of square footage and BTU/hr this is awfully small and not a large heat load compared to what the new boilers can do. That said, I do want to also ditch my electric water heater and supply all DHW via the boiler, so obviously that will be an additional load in the winter and a small load in the summer. Given the parameters, how would you design a system for this house? Just to recap:

1200SF
Design Heat Loss: 22,339 BTU/hr
All DHW supplied by boiler
System would consist of ten wall panel radiators plus heat exchanger for DHW
Oil fuel
Would like to incorporate pressurized storage

I have looked a bit into combination wood/oil units and haven't been all that impressed, but the thought of having to buy two boilers at once is a bit daunting also. Looking forward to hearing from those much more experienced and smarter than I on this subject...

 

[PassionForFire&Water]

Have a look at the Walltherm wood gasification boiler: http://www.hydro-to-heat-convertor.com/gasification.html

51,000 BTU/hr overall, of which 36,000 BTU/hr into the water and 15,000 BTU/hr radiant heat into the room.

I would use a 200 to 300 gallon thermal water storage with indirect DHW and/or an electric back up for summer.

To view this content we will need your consent to set third party cookies.
For more detailed information, see our cookies page.

Accept third party cookies

 

[Floydian]

Hey Badfish,

With a heat load that small, mini splits with the wood stove for backup start to really look good. You could probably get a couple of 3/4 ton 9RLS2 Fujitsu units(9000 btu cooling, 12000 btu heating) installed for the same price of just a decent boiler. Then you have all those panel rads, manifold, mixing valve, expansion tank(s), pumps, fittings, etc. Hydronics are great but they get expensive really quick.

Where are you located? Even as far north as Vermont it is possible to see a seasonal COP of 3 or more with the new breed of inverter driven mini splits. Plus you get the benefit of cooling even if rarely used and dehumidification which can be very important in a tight, super insulated house.

What about the windows? Upgrading or going with what you got? This might be the biggest factor in determining if simple point source heating can achieve the comfort level you want. Likely yes with quality triple pane windows and an open floor plan. Double panes and a not so open floor plan might require the more complex and expensive hydronic system you mention to get you the comfort you want.

Here is a link with info on how to do everything. Seriously! http://www.greenbuildingadvisor.com/blogs/dept/musings/how-do-everything . Martin Holladay's blogs are top notch.
Whether you are doing the work yourself or hiring it out, this site can help make sure the work is done correctly.

Also, check with http://insulationdepot.com/ about reclaimed foam goods. A year and a half ago I got some reclaimed 2.5" poly iso for about $0.65 sq ft delivered. I'd say 80%+ was in very good shape.

Good luck,

Noah

 

[peakbagger]

I ma not sure where your are located but a couple of minisplits fed by a net metered solar array with wood stove backup is the way to go. Hard to justify a wood boiler for such a low load.

If you are anywhere near Maine, give Tom in Maine a call, he has a warehouse full of foam insulation and is usually 50% the cost of buying standard sheets.

By the way with such a tight house, plan on installing an air to air heat exchanger.

 

[laynes69]

It sounds like a very expensive upgrade. What seems not adequate now (AC) after tightening up the home will act completely different after all work is done. Also placing everything in the attic, isn't always the best idea. If you currently have ductwork, I would continue to use what you have, tighten up the home, then get a smaller more efficient furnace. That's a very small heatload, maybe something like the mini-caddy would serve well, or a nice wood stove and save thousands over a hydronic setup. As far as humidity, it will increase as you reduce air infiltration. I would verify all work with a blower door test before and after upgrading. Sounds like a good plan, alot of work, but will be well worth it.

 

[avc8130]

Have a look at the Walltherm wood gasification boiler: http://www.hydro-to-heat-convertor.com/gasification.html

51,000 BTU/hr overall, of which 36,000 BTU/hr into the water and 15,000 BTU/hr radiant heat into the room.

I would use a 200 to 300 gallon thermal water storage with indirect DHW and/or an electric back up for summer.

To view this content we will need your consent to set third party cookies.
For more detailed information, see our cookies page.

Accept third party cookies

Is that available in the US? Very pretty.

ac

 

[heaterman]

Lot's of things come to mind depending on your budget.....

1st off though, you are on the right track when thinking hydronic heat for comfort. The "feel" of a house full of panel rads is completely different than the same house with a scorched air set up. There is no forced air system of any kind that will approach the comfort of a "gently warmed" water based system.

So.....if you're thinking solid fuel of some kind using a hot water system, there is no good way to do a load that small without storage. Get any thoughts of running a wood boiler alone out of your head. It just will not work.

That being the case, some of the cards on your table are possibly

1. A small wood boiler (50,000btu or less) Use a figure of 100 gallons of storage per 10,000 btu of capacity.
2. A Garn JR out in the new "man cave" heating both structures when needed.
3. The small model BioWin that modulates from about 12,000 to 40,000btu with about 120 gallons of buffer tank capacity.
(Any of the above with about 4 or 5 panel rads would offer excellent comfort levels.)

OR

4. Go with a basic wood stove in the house for the ultimate in low cost heating.

OR

5. Inverter minisplits (at a sacrifice of some comfort level and mean radiant temperature ((MRT)) in the living space).
6. Small gas furnace 95%+ rating

 

[jebatty]

I greatly respect your decision to stay small. The savings realized from a small house in real estate taxes, maintenance costs, hvac, etc. will pay big dividends in adding to your future. Show us your floor plan. That will help in providing suggestions.

What was the design low temp used for the heat calc? You may be overstating your heat loss for general space heating, and you may be able to plan space heating for a heat loss closer to 10,000 btuH with a supplement on the few really cold days. My new shop (1500 sq ft) had a design heat loss of 35,000 btuH at -30F, but normal heat loss during most of winter is closer to 12-15,000 btuH average during a day. The highest heat loss I measured was just under 20,000 btuH over a 24 hour period, and that was during a -20 to -30F period of winter weather. I measured actual heat loss by calculating btu's from the wood I burned to provide the hot water for the radiant in-floor heat.

You don't mention solar possibilities. Plan for it and do something with solar -- free heat, light, and a brighter living space. Our home is about 40 x 40 with SW exposure. We put lots of big windows across the SW side, large eaves to block summer sun but let in winter sun, and on a sunny day in January with -30F outside the house is warm just from passive solar. Very high tech window (expensive) are available that also will not result in that "window wall" not being cold or a source of drafts at night or when the sun is not shining. And the view is great, along with the free ambient lighting during daytime. Plan for other solar as well. For dark interior spaces consider solar tube lights. We have two, one in a bathroom and another in the back entry way. Now they are bright all day, every day, with no lights on, and on a moon lit night they are lit to the level of a nightlight. One time investments can have endless payback.

As for floor plan, our 40 x 40 is very open design, and we heat the entire house with a wood stove in the living room. Do you have an open floor plan or can you open it up? Our combined living room - dining room area and kitchen stay comfortable at about 70F, the three bedrooms down a hallway stay cool for great sleeping and less dry air, and two bathrooms have kick space electric heaters for an extra boost of warmth when taking a shower or bath - only extra heat when needed and then only for a brief period.

For dhw don't rule out the traditional electric hot water heater, along with possible rate discounts for off-peak or interruptible electricity. We have electric off-peak at a rate about 1/3 of the general service rate. After super-insulating the hot water heater tank and insulating the plumbing, our electric usage for dhw dropped 50%. Average bill for electric hot water now is right around $4.50 per month.

Make your changes and design for a better future - for you, the environment and all living things.

 

[heaterman]

Is that available in the US? Very pretty.

ac

Yes they are. Pretty nifty piece of equipment. 1-781-308-8583

 

[Badfish740]

Wow lots of great ideas which is what I was hoping for. I suppose it would have been helpful to tell you where I'm from now that I think of it. I live in Northwestern NJ, so getting into the higher elevations where it is slightly colder than the rest of the state, but not by much. Design low temp in the heat loss calc was 0°F, which I think is fair. From mid-January to mid-February single digit nights are not uncommon. Here is the proposed floorplan-I hope these show up large enough to read:

Main Floor-the only difference between the house and this floorplan right now is that the area on the far right is currently a garage. Everything else is the same/will stay the same after the remodel. The areas of blue fill around the perimeter are windows. The openings in the front and rear are the front and back doors.

Basement-technically all of it is unconditioned space-there are no registers serving it-only the main level. It never gets very hot in the summer so I just run a dehumidifier to keep the moisture down. In the winter, the radiant heat from the wood furnace keeps it warm.

Hopefully these pieces of information will inform the conversation a bit. I'm going to start researching the options presented thus far.

 

[Badfish740]

Ok-I just got off the phone with the folks at Pro-Fab about the Empyre Elite with electric backup. The idea of ditching oil totally is pretty appealing. Obviously I would need storage in order to use the boiler to its full potential in such a small house though. Can someone point me to a good calculator where I can play with boiler output, tank size, etc...?

 

[jebatty]

A free standing wood stove in your living room may not be within your plan, but your floor plan is quite well suited to a stove. Our floor plan is close to yours, 1500 sq ft, and we heat the entire space with a wood stove in our living room. One adjustment in your floor plan would allow a wood stove to better heat the new bedroom, but in addition to that I suggest a change in the design of your new bedroom for other reasons. Might there be an issue of excess humidity in the closet from the new bathroom? Also, might putting your entry door for the new bedroom so that it is accessed from the other end of the hall wall make sense? Less walking to get in and out of your bedroom? Relocation of the door also would allow for better air movement if you decide to put a wood stove in the living room.

 

[Badfish740]

A free standing wood stove in your living room may not be within your plan, but your floor plan is quite well suited to a stove. Our floor plan is close to yours, 1500 sq ft, and we heat the entire space with a wood stove in our living room.

I actually like that plan a lot, but one of the things my wife enjoys about the current setup (forced air oil with wood add on) is that when the wood fire dies down and the house cools off, she just bumps the thermostat up from it's default setting of 60. Then when I come home I get the furnace going again which carries us into the night, etc... Anyway I started pricing hydronics and whoever said that the parts add up quickly wasn't kidding I really don't think there's any way we can swing it. I think at this point I need to research how to expand my existing forced air system and make it work better.

 

[jebatty]

I understand your wife's point of view, and I know well the cost of hydronics. Maybe if you better show what you could do with the extra $$$ from using the wood more (wife load the furnace too and avoid use of oil) and what she could do with the extra cash, she might get in the swing of loading the wood furnace. My wife loves the wood stove in the living room so much she said "no" when I suggested going hydronic.