Pipe Insulation


I spent the afternoon putting pipe insulation on the hot water pipes in the Mill Creek NetZero Home (MCNZH). I can’t believe how cheap the insulation was – around $100 for the whole house. Its price and the ease with which it is installed make it a must, in my opinion, for those interested in energy efficiency. Anyone can install this stuff, and the insulation is so useful because it just sits and works, saving you energy every single day and never breaking.

I insulated every hot water pipe in the house except for those running to the washing machines. We virtually never wash in hot water, and the washing machine pipes were difficult to access. Otherwise, I would have gone ahead and insulated them anyway (especially the tenant’s washing machine line because you never know what kind of habits people have).

And that brings me to my one beef – the plumbers didn’t do this for us, so when they ran the pipe they made it very difficult to reach some areas. To any plumbers out there – you should offer your clients the option of insulated pipes. If you insulated as you ran the pipes (for a new home, anyway), the extra labour would be negligible.


It’s pretty tough to reach some of the pipes (the red ones are for hot water, to point out the obvious) if they have been placed without insulation in mind.

I bought “Tundra” brand pipe insulation at Home Depot. It’s made of a foam that will melt at very high temperatures, so we won’t be using it to insulate the pipes for the solar hot water system. The high temperature stuff is made of rubber, and is much more expensive, so make sure you choose the cheap stuff for domestic hot water pipes (it was about $1.50 per six foot length).




And effective.


An insulated hot water pipe in the kitchen.


Insulated water pipes in a wall cavity.

Whenever you gain access to any hot water pipe, be it while you’re doing renovations or if you’re building new, you should slap some insulation on it. Your reward will be cheaper hot water bills, less waiting for hot water when washing dishes or your hands, and a nice warm spot for you in the great eco-hunting ground in the sky.

(cross posted at raisingspaces.com)

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Because the insulation is so cheap you should consider insulating the old pipes as well.

1) It will reduce the likelihood of condensation forming on them if you have a humidity problem.

2) It will reduce noise.

3) It will stop them from “stealing” heat from any hot pipes they run next to, or in the same cavity as.

In a way you can think of cold water flowing through a pipe as very localized draught of cold air (and you are putting a lot of effort in to preventing that problem).

Some notes for your next house:
Small bore hot water pipes are often not insulated because they will lose more heat with the insulation on. If there is free airflow around the pipe there is a good chance that insulation will increase the overall heat lost from the increased surface area you may have 1/3 the heat lost per unit area but 4 times the surface area. If the pipe is very visible you should consider the long term appearance / maintenance / cleaning of the insulation. i.e. dont use it there. I wouldnt use that platic insulation unless I know its polyethylene - check for possibility of off-gasses in your very sealed house. Actually I wouldnt use any plastic unless it had a significant performance advantage. Insulating cold pipes in warm or moist areas is a good idea to prevent condensation, and you will have high humidity with your house sealed as it is. I would have paid some attention to trying to keep hot water pipes away from cold walls, and try to route cold water on the outside walls as much as practical, which you may have done.

Anyway, your house is way greener than my old clunker house and is an inspiration for all!

Interesting point about the pipe heat loss. The math is really complicated since factors involved are the radiant losses, the conductive losses through the surrounding air film, and the convective losses. I'll do some tests on my 3/4" hot water pipe to see what the surface temps are with/without insulation.

As for the humidity issue, looking at the construction pictures I suspect the house will be around 1.0ACH@50Pa. The stucco exterior finish will likely contribute significantly to the air tightness. In Jan with -25C outside and a 25kph wind the natural air change rate will be ~0.2. That will lead to dry indoor air (20C air with a -25C dew point has a relative humidity of only 3%). The first couple winters should be finde as the house dries out, but in subsequent years the humidity will likely drop below 40% leading to comfort and health issues as well.

You're saying that ADDING insulation INCREASES the rate of heat loss. That makes no sense.

Michael's comment is a bit of a red herring, but it is based on solid science. Typical domestic hot water pipes are 1/2" or 3/4". A 1/2" pipe will have ~5/8" external diameter, and if you add 1/2" of pipe insulation you increase the exterior surface area by less than 3x.
The surface air film around the pipe has an R-value of around 0.5. 1/2" of pipe insulation has an R-value of around 1.5. So the pipe insulation would help a bit, but the benefit is not huge.
With 3/4" pipe the benefit is more clear-cut; so insulating the 3/4" pipe coming from your hot water tank is what matters most.


"The surface air film around the pipe has an R-value of around 0.5." Ummm... Howzat now?

If the air film around the pipe warms ups, rises and is replaced by colder air that also warms up rises and so on and so on, how is it possible that the air film has ANY insulation value whatsoever? It will serve only to transport heat away from the pipe, regardless of the pipe's diameter. Now, put a layer of entrapped air bubbled around this pipe, preventing the .5 R value air from convecting away and you're getting the benefit of the "air film's" insulation. Funny, that's what insulation does.

I have 1/2" water pipes. Should I not bother insulating them?

Definitely insulate your 1/2" water pipes. The cost is minimal, and it will drastically reduce heat loss. For every doubling of R value, you halve the amount of heat lost. I get Michael and Ralph's point about increasing the surface area, but (admittedly without doing the math on it) I'm sure that there would still be a significant positive benefit. A benefit that pays back every day and that comes from a completely passive component..


The only way adding any kind of cover to a pipe will increase the heat loss is if the cover conducts heat. If that's the case, say you put metal clips on the pipe every 16", then Michael's comment about increasing the surface area thereby increasing the heat loss is true. In my house I have pipe runs that are only partially insulated (I ran out of insulation part way through). When in use, the insulated portion is only slightly warm to the touch and the uninsulated pipe is uncomfortably hot. Since rate of heat loss is based on the temperature difference between the hot (pipe in this example) and the cold (air), the lower the difference, the slower the rate of heat loss. Intuitively this just makes sense. If adding insulation increased heat loss then net zero houses would have walls 1" thick. Clearly this is not the case.

Insulate your pipes. As noted earlier, it's probably a good idea to do both the hot and cold lines.


Trying to say increasing the surface area will increase the heat loss would only apply if the material was the same.
The principle of insulating a hot water pipe is no different than wearing gloves on a cold Edmonton day. Next time it is -15 deg, try wearing a glove on only one hand and you will soon have your answer!

This is a job I think I can handle without calling my Oklahoma City plumber. I usually insulate all my pipes before winter, a $100 is not much of an expense considering the benefits of insulation. Thanks for giving us the tip!

Conrad, I'm surprised the plumber ran the cold lines next to the hot. The heat exchange losses would be obvious.
A few years ago, I worked for a company which builds Tim Horton's outlets in Eastern Ontario. The hot water tank was located at the rear of the building. The water lines ran up into the ceiling, across the store to the food prep areas and then down. The plumbers insulated the copper water lines with foam which was more than an inch thick. This reduced the heat losses in the long lines. This insulation could be found at Pro plumbing supply outlets.
About a decade ago, I insulated my hot water lines at home. I noticed that, in the summer, condensation formed on the cold lines. I eventually added insulation to the cold lines. Jim

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