Designing for Net Zero

or just a great HERS / ERI score.


It’s not easy to show energy code compliance in climate zones 6 and 7. Especially if you’re working in a jurisdiction that has adopted above-code requirements. Designers here’s an exercise to help get your design on its way to IECC compliance and beyond. On your next project, before starting your typical design process, rough out a schematic design, but forget all clients wishes, ARC guidelines, height limits, etc. and design for energy conservation by substituting the following parameters…


  1. Make the thermal envelope a simple, regular volume.
  2. Share assemblies with other structures, when possible, but make that party assembly very airtight.
  3. Follow the prescriptive code for air barriers and insulation levels.
  4. Maximum 20% glazing; 20-30% glazing; plan for really, really good windows, over 30% plan for great triple-pane windows.
  5. Put as much of the insulation on the outside of the assembly as you can, or frame with Efficient Framing techniques or use alternate techniques that reduce thermal bridging like; ICFs, SIPs, Larson trusses, adobe, strawbale, etc.
  6. Make the roof within 20° of optimal pitch (10:12 to 14:12) and orientation (160°-200° south) for solar, free from obstructions and penetrations.
  7. Use passive solar heating techniques when possible; insolation managed by proper overhangs and low-e coatings on glazing.


  1. Plan for no gas or propane, all electric house.
  2. Use no snowmelt.
  3. Locate the mechanical room, in the core of the house, minimize distribution runs. Give plenty of room to equipment for service. Easy access; no hatches, ladders or crawling.
  4. Locate the outdoor side of the heat pump equipment. Protected from snow and ice.
  5. Don’t use site-built forced-air ductwork if you can avoid it. Radiant or ductless preferred. If not, don’t combine ductwork with garages, ventilated attics or ventilated crawl spaces. Insulate it and seal it very well.
  6. Plan for a stand-alone occupant ventilation system, with occupant controls and easy access for filter cleaning; not in a crawlspace or attic. Ducting this is okay.
  7. Heating; use GSHP (ground source heat pump) if you can. If not, use ASHP (air source heat pump) and passive heating techniques.
  8. Cooling; skip it altogether if you can. If not, use ASHP, evaporative and passive cooling techniques.
  9. Hot water; use thermal solar per-heat if you can. If not, use HPWH (heat pump water heater). Ducting this is okay.


  1. Use no heat tape.
  2. Use ENERGY STAR appliances. Keep refrigeration loads as low as possible. Induction range and convection oven.
  3. Plan for low flow plumbing fixtures and fully insulated lines.
  4. Plan for DWHR (drain water heat recovery)
  5. If hot water runs are still long enough to require recirculation, use a smart pump with occupant sensors in the bathrooms and a temperature sensor to control the pump runtimes.
  6. Maximize the PV array size.

Designers: Now you have a schematic design optimized for potential energy conservation. As you move on to your typical design process, keep this design in the background. Know that the more your design develops away from the energy conservation architype, the harder it may be to reach specific performance goals.

Note to Structural Engineers: Your challenge is to help the Architects keep as much steel and wood out of the thermal envelope as possible. Support several inches of Continuous Insulation, even behind stone veneer. Keep the foundation completely covered in insulation, even at patios, doors and behind stone veneer.

Note to Mechanical Engineers: Your challenge is to help the Architects reduce all equipment loads, reduce runs and maximize efficiency. Investigate new technology and equipment and learn how to work with it. And help us all reduce a house’s dependence on gas.

Successful transition to the 2021 IECC

What do we need in place to ensure a successful transition to the 2021 IECC?

Designer and plans examiner education

Architects, mechanical and structural engineers need to be taught high-performance construction techniques. An IECC compliance sheet needs to be created and submitted with Construction Documents. This will help front-load the submittal documents with a more developed mechanical system, air sealing details and specifications. Plans examiners need to learn how to recognize energy conservation issues from drawings a flag them for correction before permit issuance. Once something like a weak party wall assembly is permitted, we’re on the defense for the rest of the game.

General and subcontractor education

Contractors need to know what passing work looks like, preferably before they fail an inspection. The half-dozen raters in the valley cannot be the sole education force for thousands of contractors in the valley. GCs need to know how to interact with a rater; what to include them on, what do they need to see, when to call, etc. Subcontractors need supplemental training on ERV installations, air sealing, Radon barrier installation, etc. New technicians need to be trained on heat pump equipment. I don’t believe there are nearly enough qualified people to install all of the heat pump systems we need to install in the near future. And if it is not done perfectly, the equipment won’t live up to its potential.

Homeowner education

Homeowners need to left with a document that explains how to work the house. Most homeowners seem to be clueless about how to operate an ERV for example. If a homeowner never adjusts the ERV flow or disables it completely, or never changes the filter- we may have done more harm than good in the end. Is the filter replacement schedule being posted? Outdoor reset sensors are now required- are the reset temperature curves being programed before the occupants move in?

Product availability

Builders tend to use the products that the local suppliers carry. We need to start building with products that are not typically stocked in the valley to my knowledge. Specifically I am thinking of items like; airtight electrical boxes, drywall clips, HPWHs (heat pump water heaters), small disposable spray foam kits, liquid flashing, high-performance ERVs and ventilation controllers, vapor-retarding latex primer, etc. Somehow, we need to lobby all of the hardware stores and lumber yards to consistently stock these essential products before significant demand is here.

Enhanced inspection schedule

Rater inspections need to added to inspection checklists, far too many projects go uninspected simple because Raters are not notified of the construction schedule. Ratings only technically require two field inspections, but the reality is that two is not enough. Additional inspections should be required.

  1. Pre-test ducted systems at rough-in, prior to insulation, using 2021 IECC standard, even if all ductwork and equipment is in “conditioned” space.
  2. Blower Door & IR Camera at rough-in, post spray foam in roof and walls, but prior to installation of blown-in or batt insulation. If the home has a vented attic, do visual walk-thru with insulator to identify additional air sealing required, then use Blower Door: 1) As soon as drywall ceilings are hung and fire taped, but prior to hanging drywall on walls. Or 2) As soon as all the drywall is hung, finished, and painted; but before any cabinets or trims are installed.
  3. Insulation Inspection when all insulation is complete

Rater-Building Department coordination and cooperation

Raters and Building Inspectors should have a clear understanding of who is checking for what. In the course of rating a house, we check and test a multitude of things; insulation installation quality, infiltration rate, ventilation rate and watt draw, duct leakage rate, pipe insulation, etc. Typically, JHAs ask me only for a certificate and a blower door test report. Getting an infiltration report without a ventilation report, really doesn’t give you the whole story. So far, ventilation is often being done fairly poorly in the field. There is massive confusion between occupant ventilation, crawlspace ventilation, spot ventilation and make-up air supply. I’m afraid we may see an epidemic of mold erupt in our valley in the near future. And lung cancer caused by Radon.

If the JHA does not ask me for the reports, then I assume they are doing those tests and inspections themselves, or they have a departmental policy not to enforce those parts of the IECC.

Final inspection, confirmed rating certificate and CO

Raters are often unmercifully pressured to cough up a certificate immediately at final. Raters need to have a complete, finished house to do our final inspection and test out; PV on the roof, ERV commissioned, every last piece of pipe insulation installed, door handles on and trades out of our way for testing. After our inspection, it takes a day to update the model and submit all of my paperwork. The it takes a day or two for the Rater to get the final certificate from their provider and transmit it to the General Contractor. GCs need to build this time into their schedule, it is not an instantaneous process.