Load calculation questions
We have just hired a ResNet rater to complete room by room load calculations in our new home (CZ4, humid), prior to interviewing HVAC contractors.
The first load calculations are about 73k BTU peak heating for the whole house. Our goals are thus 1) confirm model inputs and 2) identify envelope upgrades to lower peak heating load to 60k, so we can pursue a 5 ton air source heat pump. We’d consider zoning but are not sure hoe much this would increase efficiency or comfort with ASHP.
We like and trust the rater, just confirming a few things with the experts here:
1. What is R value of thick (12-18″), below grade poured concrete basement walls? (We estimated R7 due to insulating dirt and reduced delta t below grade.)
2. What is R value of this wall assembly: 12″ stone and mortar exterior + cinder block + furring strip/drywall? (We estimated R4.5, with 1.5 for the stone, 2 for the cinder block, and 1 for the drywall, but the whole assembly is leaky.)
3. Do we really need to plan for heating closed crawl spaces connected by vent opening to conditioned basement space? (Current calculations treat this space just as any other space within the envelope.)
4. If we go with an ASHP in the basement, will we be able to cool the second floor? Heating this winter was no problem (hot air rises), but I’d like to hear from others who have successfully cooled from 2 floors below, before adopting the approach.
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