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Getting away without a mechanical room (Zone 6A)

MishaB | Posted in Green Building Techniques on

This project is located in a central location in the Toronto area. The site is on a main-street backing to a laneway (alleyway). There is an existing townhouse that will be retained. The new building is accessed from the laneway; it has a walk-out basement with a unit of approximately 350 SF and one three-storey unit above 1100 SF.

The 3-storey unit is organized with 1 bedroom and a small office at level 1, 2 bedrooms at level 2, and living, kitchen dining at level 3. Half the third level has double-height space, and the other half has a rooftop terrace above.

It’s a very tight site at 12′ wide with a relatively small separation from the existing townhouse. I am the architect and owner of the project.

I would like to get good results in terms of energy efficiency, but since the units are relatively small, optimizing for living space in a central area will take priority over energy efficiency.

There is somewhat limited space for mechanical equipment outdoors – there is a very small outdoor area at-grade between the two buildings. a small front yard, and the rooftop terrace.

The main question is – how can we minimize the need for allocating floor area for mechanical equipment indoors? Addressing heating/cooling/dehumidification, ventilation, and water heating, assuming I did not miss anything. The typical ceiling height is approximately 9′ so there is some room for equipment and ducting.

I’m happy to go all-electric – which also seems to be the only way to do it. We’re Ok with mini-splits if that’s the best approach. Zoning is preferable for conditioning and ventilation, as rooms may have their doors closed for long periods of time. Filtration of incoming outdoor air is important as we are close to a high-traffic street.

The question is both about principles and approach, and specific equipment that is available in the area.

As always, the cost is a consideration, but comfort, efficient use of space and operation costs are more important.

We are now going through municipal approvals where we don’t show fully a detailed design but considering the constraints of the site, I’d like to gain as much understanding of the limitations as possible.

Thank you!

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  1. Expert Member
    Akos | | #1

    Definately can get away with no utility room.

    Slim ducted units can easily be mounted in the ceiling of a hallway or above a closet. The units are only 8" thick so it works out to about 12" bulkhead to clear. It does make a 9' ceiling feel low, so take care of where you place it.

    Another option if you don't mind going with 7/8 or 1 1/8 subfloor is to spec a section with the joist spacing is at 32" or 48" and install the unit recessed inside the joist space. I've done this for ERV units before and works quite well as there are no visible ducts. 32" is tight but doable, but with 48" spacing, fitting a ducted unit should be no problem.

    Doing 2 stories with a single ducted unit against the ceiling is pretty easy but 3 requires a lot more ducting. If your living space is open, might be better to have a wall/ceiling mount there and a ducted unit for all the smaller rooms.

    The basement apartment is too small for any fancy equipment. I would go with a wallmount for AC+heat with resistance heat in the bathroom and bedroom.

    The simplest water heater is an electric tank in the basement, which does need some sqft. Gas tankless unit seems like it would take up less space but because of clearance plus service space, it is not all that much less.

  2. walta100 | | #2

    A 36kW tankless electric water heater takes very little space and would fit nicely on the wall above the toilet just be sure to plan for the 400 amp electric panel it will require. No it does not use any more electric than a tank unit it just uses more but for less time so the watt hours are the same.


  3. Hawnes | | #3

    I currently live in a townhome that is 3 floors.
    The Rheem electric water heater is in a closet in one of the bedrooms on the second floor.
    The HRV is in the ceiling on the top floor (one of the closets of the master bedroom).
    Heating is baseboard heating (which I hate).
    There is no cooling unit.

    So there is no mechanical room, and the bottom floor which is the living area and kitchen and dining room with powder room.

  4. user-2310254 | | #4

    Some models of natural gas tankless water heaters can be mounted on the exterior.

    On the HVAC, there are minisplit heads than can be recessed into ceilings with 8 inch joists.

  5. charlie_sullivan | | #5

    There are good options for electric heating and cooling with no mechanical room: mini-splits, ducted or ductless; or air-to-water heatpumps, which have similar characteristics but allow using a larger number of smaller cheaper heads to completely avoid ductwork yet provide heat to every room.

    The challenge is water heating--to do electric you need very high current electric service. and it's not nearly as efficient as using a heat pump. So if you can find space for a hot water tank somewhere, that's your best bet for efficient hot water supply. You could use a tank with a built in heat pump, or use and Sanden system with an outdoor heat pump supplying an indoor tank, or if you go with an air to water heat pump for heating and cooling, use that to heat the hot water tank too.

  6. MishaB | | #6

    Thank you, everyone! That's been very useful.
    I'm looking forward to coming back with more questions as the project moves forward:)

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