By Marc Rosenbaum
I’m excited because I’ve been putting together a new online course on Deep Energy Retrofits (DER). More so than the course I teach on Zero Net Energy Homes, it’s focused on the multiple approaches and techniques for taking the diverse building stock we have and transforming it – not just from the standpoint of energy use, but also upgrading comfort, health and safety, and durability – because so much of our building stock is plagued with deficiencies. Retrofits fix the issues with the building asset and saving energy almost ends up as a desirable byproduct. There are so many different buildings and conditions, and therefore solutions, so the DER course is based on case studies and we show many approaches people have chosen to implement.
If energy saving is the principal goal, it’s important to look carefully at the choices the occupants make. Energy in buildings goes to more than heating and cooling, which are the main loads that retrofits target. Over forty percent of primary energy in US homes goes to non-thermal loads. Once we super-insulate a house in New England, energy for heating, once the largest load by a comfortable margin, may become the smallest load amongst heating, domestic hot water (DHW), and plug loads/lighting/appliance loads (PLA). To get to truly low energy performance then requires focus on DHW and PLA.
With motivated occupants, it’s possible to get deep energy reductions without DERs. People can do a moderate weatherization on a house, then install a point source heater such as a single zone mini-split heat pump to keep the most-used part of the house comfortable. The rest of the house runs cooler and the main heating system stays off until the outdoor conditions get severe. Lots of savings have been demonstrated in this approach. Couple that with LED lighting replacement in high use fixtures; great low flow showerheads like the Delta H2OKinetic; a horizontal axis washer; and depending on the household size, perhaps a heat pump water heater. Replace the dryer with a drying rack and a clothesline. Make a concerted attempt to keep appliances and entertainment stuff off when not using it. Hunt down phantom loads.
Combine all of the above and the total outlay might be $10-20,000 and the energy saved might equal or even exceed what a second household might achieve that goes the whole enchilada and does a DER, if that second household is much less conscious of their DHW and PLA usage, and heats the whole retrofitted house to comfort temperatures. I definitely see DER households using a pretty wide range of energy per person. The climate doesn’t care how we each reduce our consumption, just that we do. Of course a motivated, conserving household in a DER will have the lowest energy usage of all, but if a household is committed to reducing their carbon emissions, they needn’t spend six figures to get there. What the DER gets that the targeted weatherization, behavior-based deep energy reduction strategy may not is relief from the non-energy deficiencies – ice dams, pest infestations, water issues, mold, etc., and true comfort. The cost of remediating those defects shouldn’t have to be paid for solely by the energy savings that accrue.
I live in a zero net energy DER after previously weatherizing a pretty good house and also reaching zero net energy. I like the second house a lot better, because of its superior comfort and air quality. But I spent a lot more money to get there, and the total energy performance isn’t much better, because DHW and PLA usage is pretty similar. The DER uses less energy for heating at an even 70F setpoint than the pretty good house used with some temperature setback and letting parts of the house get cooler. I hope to live in this retrofitted house for a long time, and it’s worth it to me to have spent what I did to get a house my wife and I are so pleased to inhabit. I’m just not fooling myself that I needed a DER to achieve deep energy reductions, if that was my only goal.
To learn more about the transformative possibilities of Deep Energy retrofits, please check it out at http://bit.ly/DER-course. Read more from Marc’s blog at http://thrivingonlowcarbon.typepad.com/ or at South Mountain Company’s website, www.southmountain.com.
Marc Rosenbaum, P.E. is a long-time student of making great buildings. His work has been recognized nationally by ASHRAE, AIA, EEBA, and NESEA, but they didn’t see all the mistakes along the way.