Upgrading HVAC Mechanical Systems
Hello – I recently moved into a 1920’s craftsman in climate zone 4a. The house is very leaky and has a pretty old boiler heating system. I’m eligible for some helpful rebates and financing options through our utility company and I have a somewhat sensible budget to work with from the sale of our previous house. I feel that I have a good grasp (and reasonable expectations) on what has to happen in terms of air sealing and insulation but I’m still very much in the weeds on how to approach the mechanical system.
What I have:
– I did a blower door test with an experienced friend yesterday; 5500 @ 50 with the basement door open 4500 without. Square footage is about 2800, I’m guesstimating the envelope surface area at 6,590 sq ft and volume at 43,560 cu ft. Seems to come out to 8 ach.
– Gas fired atmospheric vented hwh from 2001 (poorly vented)
– 140,000 but Boiler from the 90’s
– Cast iron radiators in parts of the house, but most of the main living areas are hydronic baseboard heaters.
– No air conditioning
– Solar array that produces on average 4200 kWh per year
Proposed upgrades on the table:
– I have a good proposal for air sealing and increasing insulation in the usual places. Based on the wisdom available on this site I’m assuming these efforts could result in a 20-30% improvement in air leakage. There are A LOT of big holes to fix (which is good in a way) but I do realize I’m very unlikely to ever get to something like 3 ACH with the budget I have.
– Replacing the hwh and boiler with a Bosch combi unit – $13000 https://www.supplyhouse.com/Buderus-ZWB-42-3-Greenstar-151-117000-BTU-Combi-Gas-Fired-Wall-Hung-Condensing-Boiler
– Ducted heat pump HVAC system. The details of this are still being worked out but I’ve received one proposal for a 5 ton system with two air handlers for $35000
What I’m hung up on:
– The existing baseboard heaters heat the air though convection, which leaks out of the house pretty aggressively, currently if I set the thermostat in my living room to 70 it gets toasty, the thermostat clicks off and the room only holds the heat for about 20 minutes. Even improving this by 30% only gets me to 26 minutes. I could upgrade the baseboard units to panel radiators, I think I’d need about 10 units at ~ $500 a piece.
– As there’s no AC, I really hope to be putting in some sort of system that would include a compressor, ductwork, electrical work etc. Given that it’s an existing old house a big central air handler and big ductwork system would be difficult. Which brings me to a zoned heat-pump system at which point I’ve also got heat. I’m all for belt and suspenders but paying for two premium heating systems seems foolish (maybe it’s not, I could be wrong, I often am)
So my questions are:
– does upgrading the boiler make sense if I’m buying a heat-pump system?
– given that the house came with a solar array does it make sense to move toward electric? Install a hybrid hwh and heat pump hvac and keep the old boiler for worst case scenario back up heat?
Thanks in advance for any advice
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