Heating Systems

I talked with Johnathan Jones last night about heating systems. The current system is an oil-fired furnace (Armstrong Air Basement Lowboy 83% efficiency unit 57,000-72,000 BTU nominal output) from Sept. 2003. An un-insulated duct network in the basement serves 10 registers at floor level.

Existing heating ductwork

A few things stand out in this analysis. First, we are heating the attached greenhouse! A round dryer vent has been crudely tacked on to the system to push hot air outside. Second, the vent under the window in BR2 doesn't appear to be connected to anything. The third thing is unimportant comparatively--the return air duct seems to run much longer than it needs to. (It could come up in the wall behind the thermostat, for example.) Finally, notice that the supply duct runs under the unheated porch; all the ducts would benefit from sealing and insulation.

We're taking out the oil tank, so we need a new heat source. We could simply swap the oil furnace for a high-efficiency gas furnace and continue to use these ducts. In this case, we would want to improve the duct network.

The alternative is to remove or abandon the ductwork and install a different system, including:

• Hydronic (circulating water under the floor)
• Mini-split heat pumps
• Electric baseboard
• Electric heaters (like BR3)
• Some kind of hydronic baseboard

Update 2/11/15: I spoke to Zach at Northwest Mechanical. I think hydronic is the way to go. They have German made, computer controlled, wall-mounted boilers that can handle hot water for the house as well as heating. You run flexible Pex tubing where you want heat--floors, walls, or through slick European radiators. The radiators look like easily-cleaned plastic boards held off the wall, but they have towel-warmers that heat the bathroom, and they can even do floor to ceiling louvered room dividers.

Zach showed me a product called Joist Trak that can be installed under the existing sub-floor, between the joists in the basement. It's an aluminum track that holds the tubing and radiates the heat through the floor. Obviously, if I'm circulating heat in tubing, I can easily run it to radiators in BR3 and Ba3. I looked inside one of the existing ducts, and it's pretty disgusting. The black dust I was seeing in the MBa toilet was coming from the exhaust fan--proved by keeping the lid closed and, voila, no dust. I don't want to circulate air through ancient, uninsulated ducts any more.

We could also remove the existing hardwood (and tile and carpet), install tubing on substrate (e.g. Quik Trak, from the Joist Trak people), and then pour something like Gyp-Crete and get a smooth, continuous finished floor. I'm a little concerned about a flexing floor causing the concrete to crack, possibly causing a leak in the tubing--it's like saying you're worried that the plane might crash. It's not supposed to, there's a lot working to keep it from doing that, but... The other reason I don't want to do this is that the ceiling is already at 7' 9"--I don't have 2" to spare.

BR3 is a different situation, however. I could put tubes on the concrete, then add Gyp-Crete. This is another benefit of a hydronic system--it can be designed to run heat under the floor, over the floor, through a radiator, whatever--mix and match.

Zach Burgett
Northwest Mechanical
3204 NE 145th St (at Lake City Way)
Shoreline, WA 98155
zach@nwmechanical.com
206.267.HEAT  -- mobile: 206.255.5699