9 Comments

1. 
   scott_tenney | Nov 16, 2022 09:26am | #1

   Beautiful home. I love how you've remodeled but maintained its original character. I was a little surprised that you were able to achieve passive house certification with floor to ceiling windows in the new addition. I had always thought that large windows like that would make passive house certification really challenging...?

1. 
   Trey_Farmer | Nov 17, 2022 10:56am | #4

   Thanks Scott! It was a challenge. We have great downtown views and the site slopes away from the home to that side so it was just a thing we made a priority. It meant losing some glazing elsewhere and we were a little over the PHIUS recommended 18% window to wall ratio so had to make up for it elsewhere. The certification is based on an energy model so there are lots of levers to pull (add more insulation, make it more airtight, get more efficient equipment, reduce glazing elsewhere, etc).

   Also Texas (we are climate zone 2A) has pretty low design temperature deltas compared to cold climates (110-70 is only 40 degrees and its rare we actually get over 105) so we can get away with some things that other climates cant.

2. 
   jameshowison | Nov 16, 2022 03:51pm | #2

   Awesome stuff. This is the house discussed on the Postive Energy podcast too: https://positiveenergy.pro/building-science-podcast/2022/9/26/proving-passive-house-is-practical-possible-amp-promising-in-climate-zone-2a

   Is the service access to the HVAC from below or from the (conditioned) attic (ie from the side). Looks like from below? But then the dehu is above the HVAC, so maybe access is all through the attic.

   Can you share how long the HVAC lineup (return 90 to end of the supply plenum) is? That's got the supply-from-return duct for the dehu, then the air-cleaner, then the Mitsu unit (SVZ?), then the plenum. Is that 10' long? I'm asking because HVAC contractors have a certain length in mind, then as one seeks to add other things like this, just physically fitting it all becomes a major issue.

   I guess the real advice is "do it all in revit" but did you have an entirely clear attic structure here? ie this is hand-stack framed, not trusses (or did you model the trusses in revit, to know that all this lovely ducting would fit)? Are these the real paths of the ducts, or is this schematic?

   Is the passive house modeling available?

1. 
   Trey_Farmer | Nov 17, 2022 11:03am | #5

   Thanks for the link to the podcast :) Yes advice is to work with a badass engineer at Positive Energy hah!

   The roof is stick framed (2x12s) and the old house had a big vented attic so when we moved the insulation up to the deck we got a nice big conditioned storage/mechanical space (its 14' wide and the low eave ends are about 5' and it is almost 9' at the peak). Half of it is a loft over the guest/play room that I use as my home office, the other half is the mechanical space and storage so there is a lot of room up there to work with - so the access is walking from my office through a full sized door. I would say the lineup is probably 10' long, the room is 14' wide and it pretty much goes the full width with the ducts. Matt Risinger did a long video with Miguel from PE up there walking through the system back during construction if you want to do a deep dive:
   https://www.youtube.com/watch?v=8f6Ih09uaDw

3. 
   refereedjournal | Nov 16, 2022 05:28pm | #3

   This seems like a really neat project, but the situation you've described is not one widely applicable to historically designated (and regulated) structures.

   What you've done is preserve the historic street-facing exterior elevations while replacing almost all the materials. In my jurisdiction, this level of intervention would be considered a demolition and triggered some kind of aggressive design review process where the answer is usually "sorry, no.". I'm glad your city allowed you to do something reasonable with your house.

1. 
   Trey_Farmer | Nov 17, 2022 01:19pm | #7

   That is a good point. Historic preservation is a tricky nut. We work with our local preservation office a lot and have a good relationship with them which helps. We have found that on these old stick frame craftsmen in Austin it is really hard to keep much of the original materials. We try to whenever possible to keep original materials and intended to keep all the original framing with our house, but once the framing was exposed there was termite damage, rot, balloon framing, no headers or jack studs, etc - so we ended up rebuilding most of the framing - which is what happens more often than not down here. Im not sure if that is specific to hot humid climates being really hard on old wood homes or if that is also the case elsewhere.

   This house just won an award from our local preservation non-profit so there are definitely ways to build high performance and play within the preservation rules.

1. 
   dan7210329 | Nov 18, 2022 11:09am | #9

   Recently in St Augustine, FL, I inquired if any of the wood in old structures was original. Response: only one small school house has survived - made completely of local cypress. Your article here got me wondering if there's a materials shortage of rot resistant woods needed to replace rotted woods in historic structures in warm/wet climates. Are there rot-resistant trees planted in managed forests and how much the market would support the extra cost of rot resistant wood products.

4. Expert Member
   MALCOLM TAYLOR | Nov 17, 2022 11:52am | #6

   Trey,

   A very thoughtful project all-round. That you managed to get Passive House accreditation while still maintaining such a high quality of architecture, where there are no apparent compromises, is a real achievement

1. 
   Trey_Farmer | Nov 17, 2022 01:22pm | #8

   Thanks Malcolm, I really appreciate that!