[Greenbuilding] Water heater timer energy savings?

[John Straube]

Dan
The loss equation is
Heat Flow = Area * Temperature / R-value
So, the statement that there are diminishing returns is absolutely true
But the claim that you wont get energy savings is flatly, provable, unquestionable false.
Going for 16" of cellulose insulation to 32" of cellulose insulation will cut heat flow through the ceiling in half.
Now it is entirely valid to ask, is that reduction worth the cost, the hassle, the environmental investment.  But making such decisions with the false belief that it does not save energy results in bad decisions.

How does this apply to hotwater heaters?
A top of the line water heater will have insulation of 2" of foam which in service performs at maybe R14, likely less.  The old fiberglass insulated tanks might have been insulated to as little as R-5, but many where insulated to R-8 or so.
Adding R-10 any of these tanks will significantly reduce the heat lost on standby. By over half for an old tank but by about a quarter even in a new best in class tank.
As noted, the heat loss through piping is significant, so ensuring that there is a loop to avoid thermosiphoning and some insulation along pipes is definitely important before going beyond standard modern quality tanks.


From: Greenbuilding [mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of Antonioli Dan
Sent: April 9, 2016 22:11
To: Green Building <greenbuilding at lists.bioenergylists.org>
Subject: Re: [Greenbuilding] Water heater timer energy savings?

There's only so much insulation value you can get per application. I don't have the "calories" per calculation, but insulation has its diminishing returns. 14-16" of ceiling insulation is about all you're going to get from that application....some people think that if you keep going up into 2-3 feet that you'll get more energy savings and it's not true. That said I won't want to go down an insulation rabbit hole. The post, once again, is about digital timers and integrated watt meters. If you want to start another discussion about insulation please do.

Dan




On Apr 9, 2016, at 6:48 PM, Reuben Deumling <9watts at gmail.com<mailto:9watts at gmail.com>> wrote:




On Sat, Apr 9, 2016 at 5:12 PM, Antonioli Dan <solardan26 at gmail.com<mailto:solardan26 at gmail.com>> wrote:
Most modern hot water heaters do not need blankets as they are redundant, and redundant insulation doesn't do much.

Hm.
I'm looking forward to Rob Tom's response to that.
As for me, I'm not so sure about that. I can well imagine that some modern water heaters are better insulated (but probably not as efficient as some older designs), but how can adding more insulation with a payback of 1 year or even five years be redundant? I can't imagine that the embodied energy in a bit of fiberglass (or recycled jeans) would tip the scales.

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