HVAC – Smaller HVAC for better than code insulation?
First off, – New home, climate zone 6A – pretty good home – target <1.5ACH50. My HVAC guy provided me with manual J calculations for sizing the HVAC system and I noticed he just used code insulation values and average house build quality to determine the loads. When I asked him to re-run the numbers for my actual insulation values he said he could do that but it won’t make any difference to the hvac system he installs as it will make no difference to the equipment installed. I find it very surprising that running about 30% better insulation in the walls and 60% better than code in the roof that it has zero effect on my HVAC. Do I need to find another HVAC guy or does this make sense? FYI Roof as planned ~ R-68 Above grade walls as planned ~ R-33 Basement walls as planned ~ R-24 Windows are all about ~U-0.3 Door are all about ~U-0.4 Windows are about 20% of my total wall area (above and below grade). Steve
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