Any thoughts on honeycomb shades for windows?

Q: I have seen these claiming R4.7. Any thoughts?

A: I think they are a very good idea. They are cheap, look good and are very effective. Also, thick, pleated, lined curtains that go to the floor (or window sill) can add R3-R5 to any window. Window inserts can add R1-R2 to any window, but they also block drafts which neither shades nor curtains can do. Many older windows, especially sash windows, leak like sieves, so for these the window inserts are probably the best idea, but if your windows are not drafty then I think either curtains or shades work great and are pretty inexpensive.

Heat Pumps for Hydronic (forced-hot water) Radiator Heating Systems

Q:  For homes with existing hydronic (hot water) radiators, what do you recommend?  Is it possible to use air-source heat pumps to heat the water on those systems?  What about increasing the radiator sizes to operate with Lower water temperatures?

A: Yes you can do this. Daikin, Jaga and SpacePak all make air-sourced heat pumps designed especially for FHW systems. I think it will be a lot cheaper to use the existing radiators and leave the old furnace in place in case the heat pumps can’t keep the place warm in the middle of winter.

Questions to ask a solar-panel installer:

  • For how many years does the manufacturer guarantee the panel-power output?
    • Can I make a claim using only the data on the monitoring app, i.e., without having to get the panel independently tested?
  • For how many years does the installer guarantee the array-energy production per year (in kWh / year)
  • What is the cost per kWh of the electricity guaranteed to be produced over the warranty period of the panels?
    • Cost should be after the federal and state subsidies
    • 5c/kWh is very good but even 10c/kWh is still a 55% cut and it is fixed
  • What inflation rate did you use in the financial forecasts? If it is more than 3% ask them to redo the calculations. I used 0%.
  • Did you allow for taxes on the SMART subsidy? SMART is taxable income.
  • For how many years is my roof guaranteed against leaks?

Questions to ask a heat-pump installer:

  • Does the Manual J show my house will be at 70℉ when it is 5℉ outside?
  • If you have no ductwork ask, “Can you quote this 1) with ductless units and 2) with ductwork in the basement for the ground floor plus ductwork in the attic for the upper floor?” Also ask for a quote for radiant-floor heating, this was surprisingly cheap in our rental house (but this will not do AC for you). Make sure the attic work is well insulated or you will get ice dams.
  • I have not tried AC using cold water in radiators. Some manufacturers say it can be done, but I doubt it without getting pools of condensation on the carpets.
  • For forced-hot water radiators, make sure the Manual J calculation is done with a water temperature of 110℉ not 140℉
  • How much money will I save on heating if I am paying 23c/kWh for electricity? How much if I am paying solar rates (5-8c/kWh)
  • How much for a heat-pump hot water tank? How much will it save me per year?
  • How long is the warranty, does it cover parts and labor?

David Green’s House Has 4.6 ACH50 – Proving That You Can Get To Zero Carbon Without Passive House Level Air Tightness

I had a blower-door test done at my house and the result was 4.6 ACH50. ACH50 is a common standard for air infiltration and stands for Air Changes per Hour at 50 Pascals. Pascals are, like pounds per square inch, a measure of air pressure. 50 Pascals is about the pressure caused by a 20 mph wind. 4.5 ACH50 is equivalent to 1,035 CFM50 (cubic feet per minute at 50 Pascals). This means that the natural air exchange on my house (i.e., at 0 Pascals) is about 0.23 ACH (sometimes called ACH0). This means that the entire air volume of my house is replaced every four hours due to drafts around doors, windows, walls and chimneys. The natural air infiltration rate in my house is 238 CFM0.

This proves what I have long suspected, which is that it is absolutely not necessary to seal your house to the level of air tightness required by the Passive House (PassivHaus) Institute in order to cut your carbon emissions to zero.

The Passive House standard is often held up as the ideal standard for low-energy consumption houses. But I have never seen any financial analysis accompanying this conclusion. This data proves that you can cut both your carbon emissions and bills to zero (and I am making a 15% return on investment too) without the expense of creating a very tight building envelope.

Very few builders can build to a the Passive House standard of 0.6ACH50 and doing so often requires many hours of skilled labor plus the addition of an ERV (energy recovery ventilator) which, alone, can add $5,000 to the cost of the house. I know one contractor who recently did the air sealing on a Passive House project. He gets paid about 3x what a typical laborer on a construction site gets paid. Labor hours add up real fast at those rates! Hence, the Passive House standard for air infiltration can only be achieved at considerable expense – an investment that will never earn a return.

Much like geothermal, solar hot-water panels and thickening your walls with insulation, a super-tight building envelope makes energy sense but does not make financial sense.