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mini-split ductless without the J calcs on small 1000 ft. home ok?

Newbie7054647 | Posted in Energy Efficiency and Durability on

Before any improvements, such as sealing the leaks and new insulation, (ceiling and walls are done, crawl space will be done)  in our small “very leaky” home, we paid someone to do the J calculations with Wrightsoft.  He made recommendations of what we’d need for a mini-split ductless after improvements for a “pretty good” house.  I’ve gotten three separate estimates for the mini-split ductless and none so far have done the J calcs.  Should I rely on their experience for our small home, or continue with bids until I get the blower door test and J calcs from a company, or do I need to get the J calcs done again from someone not doing the bidding?  So two questions actually: (1) do I need the blower door test and J calcs done again or is it ok to rely on original recommendations, and (2) shall I trust the company doing the bidding to size it correctly without doing the J cals, or even trust them at all to do the calcs?

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  1. Trevor_Lambert | | #1

    Just based on reports I've seen here, don't trust the installers to offer an appropriately sized system. As for the first question, it really depends on how closely your plan matches your execution, and what assumptions they made when making the recommendation.

  2. Newbie7054647 | | #2

    Trevor, thank you for answering my questions! In the meantime, I've also discovered "Who Can Perform My J Calculations" and "The Beginner's Guide to HVAC", both here on this site that I'm new to. Reading them now....

  3. Jon_R | | #3

    Look into skipping all the Manual Js and using fuel bill data plus some cushion.

    1. Trevor_Lambert | | #4

      Fuel bill data isn't of much use if they are pre-renovation.

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