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.
A: If by best you mean the highest R value per inch then the rank order is SpaceLoft (R10/inch), spray foam or ISO boards (R5 per inch), dense-packed cellulose and Rockwool (R4 per inch) and fiberglass (R3 per inch). However, fiberglass is the cheapest per R value and you can install it yourself.
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.
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.