Choosing a woodstove for a small super insulated house

[Souprqt]

Greetings Heath.com Folk!

I am reaching out to you all because I need some advice. I am finishing my new house here on the coast of Maine. The house is relatively small, 1800 square feet. It is also super insulated with 11 inch thick walls and triple pane windows (our blower door test just came back at 0.99 ach50 - tight). The house has three levels - the walk out is an insulated slab that will be heated by radiant, the 2nd floor has a rough in for a mini-split heat pump and a chimney in the kitchen/dining area for the wood stove. The master bedroom has a rough in for a Runtel baseboard. At the moment, the sheet rockers are working and the only heat is coming from 2 small electric heaters which are keeping the place relatively comfy! I would love it if I could keep the house cozy even on the chilliest Maine nights with the slab on low and the wood stove going but I am afraid to oversize on the stove! I have been looking at the Pacific Energy Vista but am afraid that may be too much. I will also have to keep the air exchange in mind. I will be running a HRV.

 

[begreen]

It's possible a woodstove will be too much. What are the heat loss calcs on the house? What is the boiler output rating? That will help guide you. What ever the choice it sounds like if you have a stove you will want to include an OAK on it.

 

[pen]

In this case, I'd be looking at small catalytic wood stoves. As they can give an extended burn time on a relatively small load of fuel due to the catalyst.

 

[bertrn]

I agree with Pen, I built our house using spray foam insulation and installed an Aspen. It did well in Fall and Spring but with its small firebox I could not build a fire big enough to heat the 1850sf. After two years I installed a Fireview and now I stay warm during any season. Remember you can build a small fire in a larger stove but you can't build a large fire in a small stove. The cat is also great for making the heat last all night.

 

[dznam]

Greetings Heath.com Folk!

I am reaching out to you all because I need some advice. I am finishing my new house here on the coast of Maine. The house is relatively small, 1800 square feet. It is also super insulated with 11 inch thick walls and triple pane windows (our blower door test just came back at 0.99 ach50 - tight). The house has three levels - the walk out is an insulated slab that will be heated by radiant, the 2nd floor has a rough in for a mini-split heat pump and a chimney in the kitchen/dining area for the wood stove. The master bedroom has a rough in for a Runtel baseboard. At the moment, the sheet rockers are working and the only heat is coming from 2 small electric heaters which are keeping the place relatively comfy! I would love it if I could keep the house cozy even on the chilliest Maine nights with the slab on low and the wood stove going but I am afraid to oversize on the stove! I have been looking at the Pacific Energy Vista but am afraid that may be too much. I will also have to keep the air exchange in mind. I will be running a HRV.

We are also on the Maine coast in a 2200 sq ft super insulated and air sealed house using triple pane inswing windows and an ERV. We installed a Blaze King Ashford (with OAK) based on heat loss calcs that indicated that it would probably (hopefully?) work, given the low heat output on the low setting. As suggested above, we were worried that it would simply overheat the house. As it turns out, it has been perfect for us. We have never run it on high (other than startup) and run it on low approx. 90% of the time between Dec and March. If you have not lived in a super insulated house before, you will be amazed at the evenness of the heat throughout the structure, even when using a single location source of heat.

We have the same heating setup as you (underfloor radiant and Runtal radiators on the second floor (all cathedral) along with a mini split for shoulder (just not necessary, we have discovered) and summer cooling. We have never run the Runtals as the radiant on the first floor provides more than enough heat for the entire house. When we run the Ashford (on the first floor), it easily heats the entire house with no secondary source required. I have owned/owned a Woodstock Keystone and Progress as well as Jotul and VC catalytics. I don't think any of them would have been satisfactory in this house - the controllability and low heat output (when set on low) of the BK is incomparable. You will have 30 hour burn times throughout the winter running it on low. I'm estimating a little less than one cord for this winter! so my four cords of oak that are seasoning will have me 4 seasons ahead!

 

[DickRussell]

Here's another positive vote for using a small woodstove without worrying about overheating the place. Our house, now 4.5 years occupied, is superinsulated, with triple pane windows, insulated slab and foundation walls, HRV for mechanical ventilation, and very tight (final blower door at 0.8 ACH50. It's roughly twice the square footage as yours, though, and with just two levels. Just as you have found with keeping the house warm enough with minimal heat,. we heated ours through the 2010-11 winter with just the woodstove on the lower level running part time. The tag on it said 11-28KBTU/hr firing rate. The heat loss model said 22KBTU/hr at -3 F, although my best calc of actual is closer to 19K, but still right in the middle of the firing range of that little woodstove (Quadrafire 2100 Millenium, with OAK).

With a houst as tight as yours, an OAK likely will be good to have. I can't light off our stove without opening a nearby window if either the dryer or range hood is running. Once the fire is going well and drawing through the OAK well, we can run the dryer or range hood OK. Those exhausting devices just throw the HRV out of balance a bit to make up for any extra over what little the house leaks.

We don't run the woodstove all the time, mainly just in the evenings. The lower level, with the house set into a hill, is half surrounded by concrete wall and slab, and the size of the structure seems to soak up the heat well enough. We set the lower level thermostat on the GSHP at just 65, so it takes a few hours of the woodstove running down there to reach a point where we leave the stairway door open to dump excess heat to the upper level. We don't add more wood after the 11 o'clock news, so it just burns out some time after midnight. Without the weather cold enough, running the stove all the time likely would overheat the place.

The comment made by dznam about the even heating of the house with point sources of heat is right for houses like this. During that 2010-11 winter, with just part time woodstove heating from one source on the lower level, I kept an eye on two thermometers, one in the lower level utility space some distance from the stove and the other on the upper level quite removed from the stairway. The thermometers always seemed to read within a degree of each other. I suspect most people don't realize how much added comfort a tight, superinsulate house provides vs one that just meets code. Building a new house in a heating climate without going this route seems like such a wasted opportunity. You won't be disappointed with yours.

 

[Souprqt]

Thanks all! Dznam, I will definitely check out the Blaze King, thanks for the suggestion. Really great to hear from others who are in the same boat -I appreciate the feedback. I will let you all know what choice we make. I have heard from the dealer who sold us the triple pane windows who also has a super insulated house, that they really like the Rais stoves (also noting that they sell these as well) but holy cow, they are $$$$$! Funny you should say Dznam that you never use the mini-split. Even though we are roughed in for it, I think I may not need it at all and am considering not installing it this year.