Q: Will leasing panels still be financially beneficial?

A: Paying cash is the cheapest way to buy solar panels. Getting a loan is the second cheapest and leasing them is the most expensive. In this sense it is just like leasing a car. Unlike leasing a car, you cannot return the panels at the end of the lease. Solar leases can be very expensive compared to getting a loan but if your credit score is not high enough to get a cheap loan then leasing can still make sense. 

Q: Completely disagree with your re solar hot water panels;We’ve now had it for 12 months and have never ran out of hot water in a 2-family house with 6 residents.

A: If your hot water is entirely coming from your solar thermal panels then please let me know. Most solar thermal panel systems come with back-up electric heating element so that you never have cold showers even on bitterly-cold, sunless days in winter. So, it is possible that your year-round hot showers are created by using electricity in winter and not by using the sun’s heat. 

Q: If power from the utility is cut (storm, trees, down lines), the utility will NOT accept power from your panels.  To survive an outage a battery or generator will then be needed; savings and eco-impact are then significantly different.

A: By law, solar panels must disconnect from the grid during a grid outage. This prevents the linemen from getting electrocuted by your solar electricity. If you have a battery you can, during a grid outage, reconnect that battery and the solar panels to your house “behind the meter” (meaning still disconnected from the grid). This is what I am currently installing at three properties. Now the battery and solar panels are acting like a back up generator.

Q: What percentage window to wall area do you recommend and should overhangs be utilized to prevent summer overheating?

A: The less the window area the better the thermal envelope will be. Often houses have about 15-20% window area compared to wall area (without the windows) but our house has 42% and we still have a zero carbon footprint. This is one of the main reasons we need so many solar panels to get to a zero-carbon footprint. Overhangs are great for allowing the sun in in winter and keeping it out in summer. The optimal width of the overhand is about 3’ at 9’ height and 6’ at 18’ height.

Q: What brand of triple pane windows are the most cost effective or are you better off installing a real good double pane?

A: I found that Sierra-Pacific was very competitive for pine-framed windows (good if you intend to paint them on the inside) and Loewen was very competitive for vertical grained Douglas fir frames, which look a lot nicer than pine if you want the wood to show. A double pane low-E window can get to about R3 whereas triple pane low-E can get you to about R5. If you can get only double-glazed where you live, or that is all the space you have room for in the window frame, then adding thick, lined, pleated curtains that go all the way to the floor can add R3 to R6 to any window.

Do window inserts create condensation problems?


Window inserts will increase the amount of condensation on the inside of the existing window. This is because you are blocking currents of warm air in the room from moving past, and evaporating, the condensation. If you have a lot of humidity (you will know because there will be a lot of condensation on the windows and your towels will take a long time to dry on the rack) then it would be wise to invest in reducing it. Heat pumps control the humidity automatically but if you can’t fit them to your house, a good alternative is a heat-pump hot-water tank. This will dehumidify the air in the basement. Since humid air rises, condensation on windows is often caused by dampness in the basement. And, yes, you are right, all dampness problems get worse as the envelope is tightened up. Passive Houses, especially the early generation ones, often had dampness, mold and rot problems.  Mold often leads to asthma for the occupants of the house.

How do I fit window inserts if my windows aren’t square?

If the windows aren’t square then you may be better off going with one of the windows made from plastic sheet rather than the Innerglass one which is made from glass. The InDow one comes with a measuring kit that explicitly accounts for non squareness by measuring the diagonals as well as the horizontal and vertical parts. The frame of the Window Inserts one is so flexible (flimsy you might say) that it would probably accommodate any deviation from straight up to at least an inch, even without explicitly accounting for it. 

Q: Can I use window inserts to reduce the noise from the street?

A: Your question on sound deadening has given me the perfect opportunity to test out the sound meter I have recently bought. Using a white-noise generator on my iPhone I measured the sound deadening of the four different window inserts (see pages 129-134 in the book). As I thought, the flimsy Window Inserts one is the worst, but it is not the glass Innerglass that is the best, it is acrylic-plastic sheet Indow. This is what my perception was, but I thought it was just due to the road noise being higher on the side where the Indow is. Cutting the noise level by 20 decibels is a big reduction. If noise reduction is more important to you than thermal insulation, I would consider the Indow or the Alpina one, which is considerably cheaper and has similar noise reduction and thermal performance.

I found that Alpina was not the best value for money, the Innerglass one pays back faster. It is slightly more expensive but it is a higher R value. The table with these results is on page 133 in the book. Here is the table on the sound deadening results: