Hi All:

Just wanted to say that I’ve received some good news with my February natural gas bill!  Our natural gas consumption to date is down 20% on an equal degree-days basis versus last year!  Actual performance is a bit better than that because we’re probably using more hot water this year than last also.

The real shocker is that this bill was to heat roughly DOUBLE the useable living space! 

We’d hoped that our well-insulated addition with new hydronic heating system would give us the same heating bills for the new (bigger) combined house than we had before, but we’re actually SAVING money- that was a big shocker!

A heartfelt THANKYOU!  to everybody here who offered me help and encouragement during this process!  We’re by no means done the entire project, but what we don’t have done now can wait for time and motivation and funds without cramping our lifestyle.  We’re enjoying the new space enormously!  The energy performance is the icing on the cake!

Here are the vital stats:

Original construction:  19’x38′ 1.5 storey home w/unfinished basement, heated by gas conversion burner in original (coal) thermosiphon hot water radiant system

– 13’x38′ addition replaced one 38′ uninsulated wall w/two small original wood sash/aluminum storm windows and two (leaky, cold) knee-wall closets

– addition is 2 full storeys plus finished basement  c/w 17/11×31′ L-shaped garage

– ICF basement, 2″ foam under slab and between footings and slab (footings not insulated)

– good attention to air sealing during construction

– decent low-E/argon windows and doors, all with good air sealing characteristics (mostly casements), and one Velux skylight

– low thermal bridging conventional framed construction: staggered 2×4 studs on 2×6 plates, insulated headers, no headers in non-structural exterior walls

– entire top floor has shed roof cathedral ceiling (~ R27) with furring on the interior and (local) code-required air gap under sheathing w/continuous soffit and ridge venting

– Icynene insulation throughout, including rim joist space (also unfortunately including a bad mix leading to persistent odours in my workshop but nowhere else)

– good backflow preventers on dryer and bath fan vents

– garage/shop heated principally by woodstove, plus baseload heating (thermostat set at 5 C) using in-slab radiant, just to prevent condensation on my tools

– two existing rads removed along addition

– in-slab radiant in basement, plus staple-up radiant under new floors, no thermal emission plates, R* + radiant barrier under tubing

– Munchkin 80,000 BTU/hr modulating condensing boiler, firing both new radiant floors and existing rads

– Mr. Moltenmetal acts as a manual outdoor reset controller at present, but he’s pretty lazy, so he doesn’t adjust the setpoint temperature of the Munchkin very often

– we run 2 C warmer temperature and less nighttime setback than we did last year

– everybody, especially the cat, is very comfortable!

– our electrical consumption is up a bit, but not enormously, due to the increased lighting requirements.  The new lighting is a good balance of efficiency and comfort (a mixture of compact fluorescents and dimmable halogen accent lights)

Thanks again, all.  Though nothing I’ve done as a DIY qualifies as “Fine Homebuilding”, it certainly has been a fine process.  Aside from having an inspector who wouldn’t climb a ladder, I’ve had no trouble with inspections and only very minor re-work.  I don’t regret a minute of it.  And it was made all the more successful by the fine folks here! 

Best regards,  Moltenmetal