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Remodel – What is best practice for determining insulation and glazing numbers?

piperspace | Posted in Energy Efficiency and Durability on

Hello GBA,

I am remodeling a house in San Francisco. A portion of the house was constructed circa 1910. An addition was added circa 1985. The basement was finished in 1992. I am enlarging the house slightly by covering a porch and upgrading the heating system. I am required to show that the house will conform to California’s Title 24 energy regulations. 

In the course of this project I have used various software programs to model the house for HVAC sizing, radiant flooring and efficiency. All of these programs require input of R-values, U values, SHGC values and the like for each and every building component.  Doing this is tedious, error prone, labor intensive and expensive. How should I know how much insulation is present in a wall built in 1910?  How would the building inspector know if my T-24 model is accurate?

How do you guys deal with this and what do you consider best practice?
Thanks!

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Replies

  1. DCContrarian | | #1

    Best practice would be to look at pre-renovation energy usage and come up with a model that agrees with that.

    1. piperspace | | #2

      Thanks for your answer. Unfortunately my house was inadequately heated with a gas floor heater in the kitchen, no heat in the adjacent glass walled living room and electrical resistance wall heaters in three upstairs rooms. Assembling usage history would be tough.

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