Minimizing summer heat impacts of water heater inside
We’re “reconstructing” a 1946, 570 sq.ft. cottage down to the slab and studs.
The project is in Eugene, Ore., which is IECC Climate Zone 4c — mixed-humid, moderate winters and warm, dry summers.
The prior owner enclosed a ~200 sq. ft. porch across the south side of the house. This room is insulated and unheated, so it didn’t require a full permit. It has access by a door from the kitchen and an exterior door. The owner used a small, plug-in space heater in the winter.
The conditioned living area will be very tight with an HRV and one split head heating & A/C.
The conventional, electrical water heater was outside in a flimsy and unsightly insulated enclosure.
We’d like to move the water heater into this attached, unheated area for aesthetic and efficiency reasons. The only concern is the heat that it would produce in the summer may make the room uncomfortable.
We can, of course, create a decent-looking, well-insulated enclosure, but can that reduce the heat loss into the room adequately?
We’d appreciate any suggestions.
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Replies
If you use a heat pump water heater it will provide free cooling in the summer.
@DCcontrarian Agreed. However, this is one situation where our allocation of expenses warrants keeping a fairly new, well-functioning water heater. Our approach will leave the option of a future upgrade to future owners.
Our "Monet Pit Cottage" project is a "defensive" move because it's directly across the street from us in an older, close-in neighborhood; and the idiotic deregulation of zoning imposed by the City would allow a predatory investor to demolish the cottage and build 8 units with no off-street parking.
So, we know we'll lose tens of thousands of dollars on the project by reconstructing it as a high-quality little cottage, but we have a LOT of different areas we're investing in to achieve high levels of durability, efficiency, and air quality.
Assuming the water heater is a modern electric unit it will have almost no effect on the rooms temp.
I am concerned that you described the room as unheated. Putting plumbing in an unheated space seems like a bad idea.
If the concern is more about getting the heater out of its current location to make better use of the space consider tankless. They hang on the wall and could be located near the ceiling out of the way. The electric unit are very small but would likely require the service to be upgraded. Gas is good if you have other gas appliances.
Don’t waste money on the HRV this converted porch will never be so tight that an HRV will make sense. If you get a blower door test under 1 ACH50 only then consider it. As I recall your climate was pretty mild as there is almost no energy to recover when the differential is under 30°.
You did not ask but if the plan is to put money into the old house increase its market value to the point that the speculators are no longer see it as a viable flip. I think it will only work for a few years at best. The only real control is to retain ownership. I would remodel it as a short-term rental that would cash flow enough to cover it costs. The other option is to form an HOA and put restrictions on the properties deed.
Walta
@walta100 -- Thank you for the thoughtful and spot-on comments.
Let me clarify a few items that weren't detailed in my original post. This is definitely a "one-off" cottage and project.
We'll place covenants on the property to limit to one additional dwelling of no more than 2,200 sq.ft., no short-term rental, and a few other limitations. We've done this on other projects where we "rehabilitated" a run-down house. No HOA is necessary, the covenants "run with the land" and are to the benefit of us and any future owner of our house.
The enclosed porch had no installed heating, so it didn't need a permit. However, it has adequate wiring and insulation for an efficient portable space heater to provide occasional heat.
The plumbing runs mainly in the 2x4 walls of the original house and serves the bathroom and kitchen that are along this wall. The enclosure has 6-inch walls abutting the sheathing of the original house with rockwool batt insulation. That results in a ~10-inch insulated wall. Thus, the "K" copper pipes won't freeze in Eugene's mild winter temperatures as long as the living space is being heated during cold periods, and the water heater is in service within an insulated "box." (Keeping in mind that the water heater was previously *outdoors* in a leaky box with fiberglass batt insulation and there is no history of problems during winter.)
The HRV serves only the original space, which is conditioned. The conditioned space in the original house will be very tight, e.g., we're using SIGA membranes and tapes, gasketed receptacles, etc. My guess is that the enclosed porch space is not very tight, so we aren't going to attempt to include it in the 24x7 conditioned envelope. (When we do the main blower door test, we'll determine that accurately.)
There is no gas service, and we're going all-electric. I would prefer, true "on-demand" (not "mini-tank" instant "hot water"), but the required upgrade of the electrical service would be a substantial cost.
So ... my thinking now is that a tight "box" insulated on five sides will both avoid freezing and be adequate to mitigate any heat loss during summer.
In addition, I think we''ll design a small, sealed and dampered through wall fan that can supply some of the cooled air from the main conditioned area under control of the occupant. The enclosed porch has significant solar exposure with a lot of windows on the south wall, so it already gets very warm during hot summer periods. (We know the history of the house because the prior owner was a dear friend who sold is the house when she moved in with her daughter.)
-- Paul
Footnote: We would have preferred to rehab the enclosed porch as well, but it's "hacked" post-and-pier wouldn't pass code for "living space." Basically, we'd have to tear down what is currently usable space with modest ad hoc accommodations during seasonal periods.