Why so low?

4310 4th St has a 15.3 SEER/8.7 HSPF high efficiency heat pump system.

Today you can get HVAC equipment performance above 20 SEER and 10 HSPF.  In comparison, the performance of our equipment is not impressive.  It turns out that when we modeled the higher efficiency equipment they were not worth the substantial ($3,000-$5,000) extra cost. 

That's a little counter intuitive...but it works like this...

...the energy use for this building is modeled to be tiny because of the insulation and air sealing we do.  Therefore, dropping the energy use with more efficient equipment barely reduced the overall energy load further.  It literally is more cost effective for us to put $3-5,000 toward solar PV than toward higher efficiency equipment.

To look at it another way...we spend extra money on insulation and air sealing.  This is money we would have spent on higher performing HVAC equipment if we didn't have a super efficient envelope.

What about minisplits?

We wanted to use them, and we tried hard! 

Initially we designed this home to have one minisplit system with one "head" per floor.  Not only was one "head" per floor difficult from a distribution stand point, additionally, we would have had to install a separate ducted system for ventilation.  Furthermore, this approach ended up being significantly more costly than the heat pump system we decided upon.

What is SEER?  (Seasonal Energy Efficiency Ratio):

SEER indicates the relative amount of energy needed to provide a specific cooling output. The higher the SEER, the more efficient the equipment.  Many older systems have SEER ratings of 6 or less. The minimum SEER allowed today is 13.

What is HSPF? (Heating Seasonal Performance Factor):

HSPF is specifically used to measure the efficiency of air source heat pumps. It is the ratio of heat output to electrical power for a season.  The most efficient heat pumps have an HSPF between 8-10.  411 Varnum's HSPF is 8.7.

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