Starting My Hot Water Conservation Project

jeff88 · 08-23-13, 04:17 PM

I picked up a water heater blanket at my local Home Depot today, but before I actually install it, I wanted to double check some things.

It has an R-Value of 10. From what I have read, generally speaking 10/11+ is the best. (OK good, I'm off to a good start). I read that newer models have built-in insulation and so the blanket won't help much, so I should consult my owner's manual or the labels on the tank. I couldn't find it on the tank, but low and behold, the landlord was smart enough to leave the OM in the closet right next to the tank! Yay! The OM specifically says the blanket is "not necessary". It doesn't say I can't install one, but it also says problems are not protected if the blanket causes it. It doesn't specifically say what the R-Value is of the tank. So how do I determine what is "necessary"? I touched the tank and it was neither cold, nor hot, so without an infrared gun, I can't be sure how much heat loss there is (and I really don't want to buy one!). I bought a multimeter yesterday and it just happens to have a temperature probe on it. Maybe I can tape it up to the side of the tank and see what it says. At the same time, that reminded me of a temperature probe we have for another project. Maybe I will do one on two sides. Take a shower and see what happens when the heat starts to really kick in. One caveat, though, is that one wall of the closet is an outdoor wall, so during the winter it might get colder. A caveat to the caveat, however, is that it is west facing, so it will stay warmer than if the outside wall was facing another direction.

My next question is a matter of preferences. Here is what I bought: Frost King Fiberglass R-10
Here is what I found afterwards: Duck Recycled Cotton R-6.7
My question is this: which is better? One is higher value, but is fiberglass (boo!) and the other one is lower value, but is recycled cotton (yay!). Does it really matter which one, or is the 3.3 difference large enough to make a difference? I would prefer to use recycled cotton, especially since it is cheaper, but I don't want to sacrifice performance either.

Thanks!

MN Renovator · 08-23-13, 04:58 PM

I'd use the fiberglass R10 blanket, just be sure you tape it up well so air doesn't pass through it. My water heaters manual says it is 'superinsulated' but I carefully drilled a small hole through the outer metal wrap and then pushed a thin but strong wire(coat hanger type stuff) into the foam insulation and it was somewhere between 1.5 and 2 inches(coat hanger was a little bent). Polyurethane or extruded polystrene type foam would be about R7-R10. The longer the warranty period(higher cost) usually they will increase the insulation level. If you are lucky the datasheet on the unit will say the R value of the unit. The standards for water heaters have improved, I removed a 1990 water heater and it was 2 inches of fiberglass packed inside which probably gave R6 or so(but also puts the insulation in contact with the outer metal case which is slightly detrimental). Either way I think that adding another layer of fiberglass to your current unit even if it says you don't need to isn't a bad idea. Especially when the thicker fiberglass ones are only about $20 or at least that is how much I paid for mine. If it is gas be sure you aren't covering any air intake at the bottom, there is usually a plastic mesh. Keep it away from the gas controls and top of the tank too. If it is electric, you aren't supposed to cover the wiring chases or service covers. Don't cover your temperature/pressure relief valve either because if it doesn't work, you are in trouble.

Daox · 08-23-13, 05:03 PM

More insulation definitely won't hurt at all. The payback will be longer is all. If its one thing ecorenovators agree on its that more insulation is always a good thing.

I'd just install what you already have.

MN Renovator · 08-23-13, 06:28 PM

Daox, you just reminded me of your thread where you linked the super insulated water tank.
http://ecorenovator.org/forum/conser...ater-tank.html
I think that at my natural gas rate, even if it doubled that this much insulation would not pay off. My water heater used 4 therms(400,000 BTU) a month over the summer when I was taking incredibly short showers(2-3 minutes of water with the get wet, stop water, lather up, rinse method) and also conserving dishwashing by using paper towels, reusing plates and using hand sanitizer instead of soap, which is about $3. I had it to the point where I could turn the thermostat down to vacation for those 3 months so basically that is the usage of the pilot light. This doesn't work so well unless the house is at 80 degrees or warmer in the house consistently otherwise the showers start getting cold. Unfortunately I now share the house with someone who takes long showers so I can't test how the blanket works when it is say 60-65 degrees in the basement. She should be moving out(I hope, she leaves lights on and walks out of the shower while it is running without turning it off for minutes at a time, bugs me on many levels) in March and so I should be able to test this when the furnace season ends next year. I had a month where she wasn't home much and happened to shower at friends houses, not sure why but I was down to 9 therms($7 of gas) there with the basement at 65 degrees before the insulation was put on. I'd imagine that it could potentially save about $2 a month during the summer with AC use and likely more in the winter. I figure probably will save me what it costs in about a year. If I'm off, maybe 2 years but it seems like it should save a decent amount. Especially when we aim for R19 cavity insulation with 2x6 wood frame construction. I figure that with a 120-140 degree tank and a 75 degree difference being worse year round than a house that there is no reason not to have more insulation on a water heater.

I'm somewhat considering buying another blanket to layer over the existing one and using the leftover material and some scrap fiberglass to fill in the gap around the larger circumference of the existing blanket of insulation I already added. R20 is half the heat loss of R10 and if it isn't quite R10 to start with, you are already better off. With an electric tank, I'd say it's a no brainer, its quite a bit more expensive to heat water with electricity pretty much everywhere.

08-23-13, 04:17 PM	#1
jeff88 Lots of questions Join Date: Aug 2013 Location: San Jose, CA Posts: 73 Thanks: 27 Thanked 2 Times in 2 Posts	Starting My Hot Water Conservation Project I picked up a water heater blanket at my local Home Depot today, but before I actually install it, I wanted to double check some things. It has an R-Value of 10. From what I have read, generally speaking 10/11+ is the best. (OK good, I'm off to a good start). I read that newer models have built-in insulation and so the blanket won't help much, so I should consult my owner's manual or the labels on the tank. I couldn't find it on the tank, but low and behold, the landlord was smart enough to leave the OM in the closet right next to the tank! Yay! The OM specifically says the blanket is "not necessary". It doesn't say I can't install one, but it also says problems are not protected if the blanket causes it. It doesn't specifically say what the R-Value is of the tank. So how do I determine what is "necessary"? I touched the tank and it was neither cold, nor hot, so without an infrared gun, I can't be sure how much heat loss there is (and I really don't want to buy one!). I bought a multimeter yesterday and it just happens to have a temperature probe on it. Maybe I can tape it up to the side of the tank and see what it says. At the same time, that reminded me of a temperature probe we have for another project. Maybe I will do one on two sides. Take a shower and see what happens when the heat starts to really kick in. One caveat, though, is that one wall of the closet is an outdoor wall, so during the winter it might get colder. A caveat to the caveat, however, is that it is west facing, so it will stay warmer than if the outside wall was facing another direction. My next question is a matter of preferences. Here is what I bought: Frost King Fiberglass R-10 Here is what I found afterwards: Duck Recycled Cotton R-6.7 My question is this: which is better? One is higher value, but is fiberglass (boo!) and the other one is lower value, but is recycled cotton (yay!). Does it really matter which one, or is the 3.3 difference large enough to make a difference? I would prefer to use recycled cotton, especially since it is cheaper, but I don't want to sacrifice performance either. Thanks!

08-23-13, 05:03 PM	#3
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	More insulation definitely won't hurt at all. The payback will be longer is all. If its one thing ecorenovators agree on its that more insulation is always a good thing. I'd just install what you already have. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

08-23-13, 04:58 PM	#2
MN Renovator Less usage=Cheaper bills Join Date: Nov 2010 Location: Minneapolis, MN Posts: 939 Thanks: 41 Thanked 116 Times in 90 Posts	I'd use the fiberglass R10 blanket, just be sure you tape it up well so air doesn't pass through it. My water heaters manual says it is 'superinsulated' but I carefully drilled a small hole through the outer metal wrap and then pushed a thin but strong wire(coat hanger type stuff) into the foam insulation and it was somewhere between 1.5 and 2 inches(coat hanger was a little bent). Polyurethane or extruded polystrene type foam would be about R7-R10. The longer the warranty period(higher cost) usually they will increase the insulation level. If you are lucky the datasheet on the unit will say the R value of the unit. The standards for water heaters have improved, I removed a 1990 water heater and it was 2 inches of fiberglass packed inside which probably gave R6 or so(but also puts the insulation in contact with the outer metal case which is slightly detrimental). Either way I think that adding another layer of fiberglass to your current unit even if it says you don't need to isn't a bad idea. Especially when the thicker fiberglass ones are only about $20 or at least that is how much I paid for mine. If it is gas be sure you aren't covering any air intake at the bottom, there is usually a plastic mesh. Keep it away from the gas controls and top of the tank too. If it is electric, you aren't supposed to cover the wiring chases or service covers. Don't cover your temperature/pressure relief valve either because if it doesn't work, you are in trouble.

08-23-13, 06:28 PM	#4
MN Renovator Less usage=Cheaper bills Join Date: Nov 2010 Location: Minneapolis, MN Posts: 939 Thanks: 41 Thanked 116 Times in 90 Posts	Daox, you just reminded me of your thread where you linked the super insulated water tank. http://ecorenovator.org/forum/conser...ater-tank.html I think that at my natural gas rate, even if it doubled that this much insulation would not pay off. My water heater used 4 therms(400,000 BTU) a month over the summer when I was taking incredibly short showers(2-3 minutes of water with the get wet, stop water, lather up, rinse method) and also conserving dishwashing by using paper towels, reusing plates and using hand sanitizer instead of soap, which is about $3. I had it to the point where I could turn the thermostat down to vacation for those 3 months so basically that is the usage of the pilot light. This doesn't work so well unless the house is at 80 degrees or warmer in the house consistently otherwise the showers start getting cold. Unfortunately I now share the house with someone who takes long showers so I can't test how the blanket works when it is say 60-65 degrees in the basement. She should be moving out(I hope, she leaves lights on and walks out of the shower while it is running without turning it off for minutes at a time, bugs me on many levels) in March and so I should be able to test this when the furnace season ends next year. I had a month where she wasn't home much and happened to shower at friends houses, not sure why but I was down to 9 therms($7 of gas) there with the basement at 65 degrees before the insulation was put on. I'd imagine that it could potentially save about $2 a month during the summer with AC use and likely more in the winter. I figure probably will save me what it costs in about a year. If I'm off, maybe 2 years but it seems like it should save a decent amount. Especially when we aim for R19 cavity insulation with 2x6 wood frame construction. I figure that with a 120-140 degree tank and a 75 degree difference being worse year round than a house that there is no reason not to have more insulation on a water heater. I'm somewhat considering buying another blanket to layer over the existing one and using the leftover material and some scrap fiberglass to fill in the gap around the larger circumference of the existing blanket of insulation I already added. R20 is half the heat loss of R10 and if it isn't quite R10 to start with, you are already better off. With an electric tank, I'd say it's a no brainer, its quite a bit more expensive to heat water with electricity pretty much everywhere.