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stevehull · 08-14-15, 11:03 AM

Interesting perspective from Texas. I have a similar observation from New England.

About eight years ago, a cousin of mine was building a home (Vermont)and asked me to run a "Manual J" analysis. Did so and I noted the design temp of -35F min and a max of 90F.

I asked him when the last time he saw -35F in the winter. He said maybe back in the 1960's. How about 90F max? All the time now. In fact, the wife wants to put AC in . . . .

I did my own analysis and we got him a far better home by minimizing air infiltration, putting in an ERV for dedicated ventilation, put the dryer in a room using make up outside air and also put in basement wall closed cell foam (on outside walls). Then I did manual J (which does not have low air flow turnover rates) and did my guestimates.

The HVAC people, that did his install, were furious as my analysis showed that a 45% reduction in total BTU heating was appropriate - compared to their Manual J calculation. They were all too eager to sell him a 6 ton unit. He has a 4 ton and it works perfectly. We did put in an emergency 15 kW resistance strip and in the four years it has never been used (it is turned off in the unit).

Just as HVAC dealers are screaming in Texas that Manual J is not accounting for the now "normal" summer hotter temps, people in the north now need AC in the summer.

. . . . and educated individuals on this site don't believe in global warming . . . . .?

Steve

08-14-15, 11:03 AM	#4
stevehull Steve Hull Join Date: Dec 2012 Location: hilly, tree covered Arcadia, OK USA Posts: 826 Thanks: 241 Thanked 165 Times in 123 Posts	Interesting perspective from Texas. I have a similar observation from New England. About eight years ago, a cousin of mine was building a home (Vermont)and asked me to run a "Manual J" analysis. Did so and I noted the design temp of -35F min and a max of 90F. I asked him when the last time he saw -35F in the winter. He said maybe back in the 1960's. How about 90F max? All the time now. In fact, the wife wants to put AC in . . . . I did my own analysis and we got him a far better home by minimizing air infiltration, putting in an ERV for dedicated ventilation, put the dryer in a room using make up outside air and also put in basement wall closed cell foam (on outside walls). Then I did manual J (which does not have low air flow turnover rates) and did my guestimates. The HVAC people, that did his install, were furious as my analysis showed that a 45% reduction in total BTU heating was appropriate - compared to their Manual J calculation. They were all too eager to sell him a 6 ton unit. He has a 4 ton and it works perfectly. We did put in an emergency 15 kW resistance strip and in the four years it has never been used (it is turned off in the unit). Just as HVAC dealers are screaming in Texas that Manual J is not accounting for the now "normal" summer hotter temps, people in the north now need AC in the summer. . . . . and educated individuals on this site don't believe in global warming . . . . .? Steve __________________ consulting on geothermal heating/cooling & rational energy use since 1990