I remember the first place I lived with my mom, dad, and brother. It was an old one room apartment. In the winter it was freezing and we bundled up like we were going outside. The old single pane windows let the cold in. We didn’t use the heater much as that meant less money for food.
Most of the year I’m more concerned about not being hot so I purchased windows with the highest rating for blocking out the sun. The government ratings call it SHGC or solar heat gain coefficient. My windows were rated to block out 81% of the sun’s heat which is pretty good. It’s only cold for 3-4 months out of the year and that’s when a windows U-Factor is important. The ratings range from 0.14 to 1.20 with the lowest number being the most cold resistant. My low-E 4 door had a U-Factor of .24 which is very good. My low-E 3 hot/cold bedroom had a U-Factor of .29 which is ok.
These are some observations over the years and windows.
single pane windows – very poor insulator. Very cold or hot.
double pane windows – an improvement over single pane windows but not alot.
double pane windows with low-E glass – an improvement over double pane but still hot and cold
double pane windows with vinyl frame and low-E 3 glass – a big improvement over double pane windows with low-E glass
double pane windows with vinyl frame and low-E 4 glass – a big improvement over double pane windows with vinyl frame and low-E 3 glass
Low-E 4 glass is the state of the art in window technology where all 4 sides of a double pane window are coated to prevent heat from getting in and out. The original low-E glass I bought in 2000 just had 1 surface of the double pane window coated. Milgard calls their windows 4th surface.
It’s almost winter now and I have by checking the temperature in all the rooms and adding foam insulation as needed. Here is a sample of my readings November 20 2024 6am:
42F Outside
58F hot\cold west facing bedroom next to low-E 3 window
69F Inside living room next to low-E 4 patio door with blinds open
Having a cold room was not good as it cools down the rest of the townhouse. I was trying to figure out why that cold room was so cold and noticed the left pane of glass was much colder than the right pane of glass. On further inspection I noticed there was a tiny gap in the moulding. I had Milgard fix the gap. I also asked the technician to check if the argon gas had leaked out but he said I voided the warranty by putting a film over the window. He also said the right pane of glass was protected by the window screen so that side is normally warmer. I told him the screen was full of holes and is a terrible insulator. He stood by his statement but I checked the other windows with screens and did not notice a temperature difference.
There was a noticeable improvement after the repair. The room was 3 to 5 degrees warmer. The left pane of glass was still colder than the right pane.
At sunset I started putting up 2 layers of foam insulation on the left pane and a single layer of foam insulation on the right pane of glass each sunset. The new temperature reading:
66F hot\cold west facing bedroom next to low-E 3 window with foam insulation.
I am now satisfied with the temperatures in the hot/cold room. I’ve been checking and at 6am the room is usually 3 degrees colder than the rest of the townhouse. In conclusion I am amazed at how low-E 4/4th surface patio doors keep out the cold. It looks like I’ll be very comfortable without using the heater unless it gets down below 40F. Last year when it got into the 30’s the living room was in the low 60’s. Also the Milgard lifetime warranty is only good if you follow all the fine print.
I hope my parents are proud of how I no longer rely on the utility company to stay warm or cool.
Cool low-E glass article https://www.weforum.org/stories/2024/06/low-emissivity-glass-revolutionizing-building-efficiency/
Good job honey.
Thanks!