Q&A: A Forum for Green Building Experts and Beginners

I've been re-reading Martin Holladay's posts on water heating as I once again deal with a small-ish super-efficient house: 1900 ft2 with a heating load of less than 20 kBtu/hour. The homeowners have access to propane and electricity and here in MN, electricity is still generated by a lot of coal, although the homeowners are planning for a pv system.

At the moment I've narrowed heat/hot water system ideas down to three:
1. use a 6kW modulating electric boiler for space heat (hydronic radiant) and also to fire to an indirect tank for hot water. Also, use a drainwater heat recovery device.

I'm working on a project to rehab and convert a garage building to a studio and living space and am looking at options for exterior wood siding and decking.

I will be using Hardie Panels with reveal strips for much of the siding, however there are some areas I would like to use a clear finished wood siding for an accent. In addition I'm building a small ground level deck and want to match the decking to the siding wood. The totally square footage of wood being used fairly low at around 500 sq. ft.

I was told that my central AC needs a larger return duct. The symptom was that the low pressure line at the compressor was icing up on the outside. Does this make sense? I had thought that if the system was low on freon that this was a symptom.

I am handy but need some input into the size requirements of a return duct versus the output ducts. I would assume them to be about the same size.

Our long-term plan is to add a deck/pergola/conservatory on top of a one-story room on our mostly two story house in Zone 5a. BUT, the roof on the single story leaks and will be unshingled/re-shingled NOW. We'll use this opportunity to remove decking of the flat part of the roof (it angles from the flat part down to the three walls), access the inaccessible attic, and air seal/insulate before re-shingling.