Homeowners seldom realize that the building enclosure, heating/cooling system, equipment and energy sources are all connected. Tweak one part of the system of systems and it will create feedback loops – bad ones if the building science homework isn’t done first. It’s akin to randomly removing, adding or replacing a wire or hose from a car engine with a prettier one. Don’t do that!
Here is the ‘whole home’ building science path I’ve observed to yield the best outcome. It applies as much designing a new building as it does to retrofitting an existing one – the work is all first built in to the plans at the outset. Everything is connected.
The Ultimate Retrofit Plan
1. Do No Harm
a. Use a bona fide building scientist to make a customized plan for that homeowner/site. One size fits all is for high-rolling gamblers with a loser fetish only. For the rest of us it is dangerous and sad.
b. Get your building scientist to do a comprehensive on site home performance audit. Hint: if on site visuals, infrared and blower door are not used, it is not a home performance audit. It is a sales tactic. Especially if it’s ‘free’ and done by a company that sells ’stuff’ (e.g. solar, insulation, magical radiant barriers, shiny tech).1
c. Include one asset-based energy model that includes current / future power sources and heating/cooling load calculations. Now do another one, true-ing it up for the reality of that customer, site and build.
d. Include a plan for each of the steps below – what to do first, second, etc; what the measurable, verifiable outcomes will be, when it will be done, who will do it and how much each step will likely cost.
d. Have a plan to verify at each step that the designed outcomes match actual bids match actual build match outcomes. Yes that is three points of verification.
2. Button it Up
a. Building enclosure upgrades (lower net load/annual energy requirement including water/vapor/ice/moisture barriers, air sealing, duct improvements, insulation).2
a., Alternate: Solar typically does no harm so ok to put it first – just be careful and see the next steps and build in / have a plan for expandability.
b. Fix/replace roof if it will be used for solar (obviously before you put solar on it).
c. Outline a verification plan including a post retrofit blower door test and ASHRAE 622 / load calc.
a. Think about the electric panel & supply – upgrade in accordance with a five year plan including the following:
b. Heating, Ventilation, Cooling, Dehumidification, Filtration, Controls, Distribution upgrades (or at least understand if current systems are oversized now and/or after building enclosure upgrades).4 Electrify to extent possible using heat pump technology (use cold weather heat pumps if temps regularly go below 30 in winter). State when upgrades will be completed to avoid emergency replacement.
c. Other building equipment upgrades (water heater – heat pump if possible; stove – induction if possible; etc).
d. Get an EV! (Or rather – understand that you will probably have one and work in a Level II EV charger / Dryer share circuit. Location matters.
e. Enact verification plan including pressure test across the coils, duct tightness testing, etc.
Now that the building is as efficient and safe as it can be, size solar for long term sustainability, resiliency and peace of mind!
a. Photovoltaics on the roof or ground-mount. And because you’re smart and did step 1, you can solarize any time. 😎
b. Because you had a plan and allowed for convenient placement of batteries and panel connections at the Electrify step, add batteries sized to act as a generator (when they are cost effective or do it now if you have lots of $$$). Everything is connected. See this guide to going solar
c. Enact verification plan.
4. “Live well and prosper.” – Spock
Footnote 1: Expect to pay between $475 to $795 for a bonafide energy audit with a plan and load calcs, realizing that a skilled building scientist will be at your home for 3-4 hours and crunching numbers and your report for about twice that back at the office.
Footnote 2: This has the added benefit of making a building more comfortable, safe, resilient, durable, and lowering energy costs for heating/cooling. Doing it wrong will have dubious comfort effects and make the building more dangerous.
Footnote 3: This is where you replace any fossil fuel stuff possible – note that this will increase annual electrical usage / solar system sizing while reducing or eliminating gas/propane/fuel oil dependence. Added benefits include indoor air quality and home safety. Be skeptical any retrofit program that does not allow fuel-switching. Look for a blog post on this, soon.
Footnote 4: “Most homes think they have an HVAC system but they really only have a HAC system, while what they need is an HVACDFCDM.” – Better Building Works LLC
Everything is Connected!