Expert: Richard Taylor, AIA - 1/29/2005

Question
I plan to build a 2400 sq. ft. live-in workshop in northwest Colorado and need help with the space and water heating design options.  The building will consist of two stories, with the downstairs being slab-on-grade, and the site has excellent southern exposure.  We will use the building intermittently, and it will likely be constructed with high R value SIPs. I think I want to stay away from using gas and I'm very interested in radient floor heating, on-demand hot water heating, and solar power, but would like to understand all the options and costs before making a decision.  For example, because we will use the building only occasionally in winter, I don't know if it makes economical sense to install a solar hydronic heating system.  Can you please tell me what options are available and recommend one to me?  

Answer
Hi Keith - thanks for your question!

I'll start by telling you I can't recommend a system without a great deal more information about the project - you'll need to speak with a local HVAC engineer about that.

I can tell you the basics, however so you'll know what to look for.  The two most important factors to consider are: what is the climate like during the times when will you use the workshop, and how available are the fuel sources?  If you have lots of cloudy days in the Fall and Winter (as we do here in Central Ohio) then solar options are going to be of very little value.

The fuel source is your first consideration.  Solar works when it's there, but you still need to store the energy somehow, and solar systems are finicky and high-maintenance - maybe not a good choice if you're only going to be there now and then.  Electric is easy to get but fairly expensive to use for heating and cooling - although in an SIP house, it may be quite economical.  Heating oil may not be available, is expensive, and is a bit messy.  Natural gas and propane are prone to price fluctuations.  Natural gas may not be available, but propane is popular in more remote locations because it's stored on site.  Depending upon the soil conditions, you might consider a ground-loop heat pump system (uses underground water as the heat exchange medium).

If you're going to work there in summer and winter, and you want heat and air conditioning, then you're going to spend more money putting in A/C (coil, ductwork, blower, etc.) and the radiant floor system.  If you don't need A/C then the radiant is an excellent choice.

When you use SIPS you should have the entire HVAC strategy evaluated by an engineer, since SIPS typically reduce the heating and cooling loads dramatically.  It would be very easy to put in too much capacity!

For intermittent use, on-demand water heating is the best choice.  I suspect you've already figured this one out!

If installed cost is a consideration, then you have to limit your choices to what's readily available and understood locally.  Nothing raises prices more than unusual systems or strategies.

Bottom line:
-What fuels are available locally
-What systems make sense for the climate
-What systems make sense for how you use the building
-What systems are reliable when you're not there
-Balance the cost of cheaper but less-efficient systems vs. higher first cost but lower fuel consumption
-What systems are available locally and can be easily serviced by local technicians
-Find a local HVAC engineer to evaluate your design, location, and budget and review the options with him

Hope this helps!

Richard Taylor, AIA
Richard Taylor Architects, LLC
www.rtastudio.com