Simple Heating and Cooling for well insulated house

[John Raabe]

This low cost system uses a point source heater or AC (such as a mini-split heat pump) to provide whole house conditioning.

With a well insulated tight shell this system uses a very quiet small fan to pull air out of the house. This slightly depressurizes the remaining gaps and pulls fresh dry air into the interior. Doing this will not work well with non-sealed combustion appliances such as an older gas water heater,  fireplace or standard wood stove. However, the system provides even heat without ductwork and is quiet, inexpensive and efficient.

http://www.jlconline.com/cgi-bin/jlconline.storefront/EN/UserTemplate/69?c=09577395d1444af888bd852939195958#Basic

[dougpete]

Thanks for posting this -

So a ductless mini-split heat pump with the exhaust fans would work to both heat and cool the 2 story universal, assuming the building envelope was very tight?

Would a wood stove be completely out of the question with this system, or would there be some venting considerations?

dougpete

[John Raabe]

The problem with the wood stove in a negative pressure house is that you can pull air back down the chimney when it is smoldering or even with no fire. I can do this in my own relatively tight Solar Saltbox when the dryer is running and the cooking vent fan is running. We make sure these are off when starting a fire and generally have a nearby window cracked for fresh air to the stove. Newer stoves often have a duct for fresh air supply.

For highest efficiency from the mini-split and best distribution of the heated or cooled air you would want the chimney draft sealed off and windows closed.

I would think the Universal Cottage would be a fine efficient house for such a system. Just as in the study house, my upper level bedrooms run a few degrees cooler than the main floor and we like that just fine. Heat is controlled by opening and shutting doors rather than duct work.

[dougpete]

If you went with this type of system would you then rule out any wood stove without a fresh air intake?

The one non-negotiable in our house project is a wood cook stove......

On the other hand, we have gotten used to an indoor air temp of around 60, and I'm thinking a well insulated universal would not be too hard to heat with a wood stove.  Here in the Ozarks keeping cool in the summer is a much better issue than keeping warm in the winter.  I suppose you could go with the ductless heat pump and just use it in the summer for cooling.



dougpete

[Shawn B]

The theory they used for the project discussed in the article as been applied for many, many years; just not in the same style. Old houses with single source heating such as wood stoves, pot bellied stoves, or carburetor oil ( drip  ) stoves used to have big 18" x 18" or larger pass through cast iron floor and ceiling grilles to increase heat flow to the upstairs. My grandparents house was like this. Also the whole house fans that used to be popular worked on this principle, but were much louder and used more energy. Actually in the western States a whole house fan still makes a lot of sense for cooling, with the low night time temperatures and low humidity.

I once installed a system similar to this for a family that primarily heated with a wood stove. We cut in a 6" x "14 straight boot in a closet wall behind the wood stove. Then ran some 8" w.a. pipe, installed a small inline fan ( can't remember the brand name but was probably a FanTech or similar ) wired to a rheostat for fan speed control. Next installed a 8" x 6" x 6" Y and ran the 6" runs to there boots. The pipe was taped and insulated and the fan mounted on some vibration absorbers (rubber pads). Also we cut in a passive floor grille directly above the wood stove to allow heat to rise into the above room. The owner told me a few years later that it did help a lot more than he thought it would in distributing the heat.

dougpete......you could do something similar to the above with your system. Another thing that is quite common on homes that our designed too air tight is to install a small 5"-6" air hood on the outside and to either duct it to the return air on a forced air system, thereby it is filtered and conditioned before distribution. Since your not using a ducted system you can always duct it close to the wood stove, say behind it or similar. This would help condition the air before as it enters the dwelling. This would also help add some combustion air on a non sealed combustion fireplace.

[dougpete]

Thanks Shawn,

I'll look into having a fresh air vent in the wall which can be shut off if necessary, along with the ability to close the chimney.  I can't see needing to run both heat and wood stove, and in the summer the wood stove would be used rarely if at all.  I would greatly prefer not to have to use duct work.