Mild climate; expensive cellulose — What to do?
I am getting ready to go to Engineering for a new house in Raleigh, NC.
HDD – 3247 and going down….On border of zone 3 and 4. Technically in 4 but 20 miles from the 3/4 border.
Being in the South, everyone worries about cooling but we usually have 3x the cost in heat (based on last energy audit).
The house has a good amount of South windows. We are planning 2×6 construction and 24 O.C. I’d prefer to not do foam in the walls. Cellulose is looking like a $4,000 upcharge – for a 3700 sqft house. This is comparable to OCF. I am still waiting for the exterior rigid foam quote but it should be quite close – I’m guessing a little lower.
So here are my options –
– R19 batts
– R19 batts + 1 inch foam
– Foam or cellulose in 2×6
In a larger house with more windows that were less optimally oriented and R-13 walls, the heating bill is around $500 a year. Hard to get an exact number because of dual fuel. I anticipate the air sealing to be better this time around – we plan zip walls and are shooting for an ACH of 1-1.5 when the last house was more like 4. And all ducts will be in conditioned space – probably between floors. So I’m thinking with batts we will be more like $300 a year.
I’m perfectly happy with a 30-50 year payback but no more. I am also willing to pay more for sound control. But it seems hard to justify $4000 for cellulose or rigid exterior foam because I am thinking somewhere around $50 a year savings…..
We have $.05 per kwh at night and will likely use a heat pump and a minisplit or two. I am anticipating 2 ton heat pump with a minisplit for the master bedroom. So there is no where to save on equipment costs.
So is a pretty good house in central NC, R19 batts? And then otherwise – shade and window orientation and air sealing.
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