Mitsubishi City Multi for heat and a/c (and a question about closed cell foam insulation)

I have reviewed prior posts on this topic and am hoping for some new thoughts, particularly from those with experience with the Mistubishi City Multi or similar for both heat and a/c. We are gut renovating  a triplex (parlor, garden plus about a third of the cellar — other part of the cellar is common space) within a 5 story brownstone co-op.  The parlor floor is on average18x45 with 12 foot ceilings, the garden is on average 18×45 with 8 foot ceilings, and the cellar is about 18×15 with 8 foot ceilings. We also have the backyard, where any hvac equipment will sit. The current heat configuration has a boiler on each of the parlor and garden and floorboards for heat.  There is currently no a/c.  We are replacing all windows and planning to maximize insulation. **Closed cell foam spray has been recommended and I am curious about experiences/thoughts on this. ** With respect to heating and a/c, We are sold on the mitsubishi city multi for a/c (not the wall hung Mr. Slim but the ducted high efficiency system) and are interested in using it for heat as well given that it would be the most efficient use of space/equipment.  If we continue to use boiler for heat, we will need to move it to the common area of the basement and replace all floorboards with radiators.  I am concerned that the city multi will not provide sufficient heat.  I know people warn against this type of system because they say that it is dry and that radiators are better, but I have had good experiences with forced air in my old condominium and bad experiences with radiator heat (as currently, in my office, which feels like a sauna).   Any thoughts and experiences woudl be greatly appreciated.  Thanks in advance.

karenanne9

in Insulation 12 years and 4 months ago

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brucef | 12 years and 4 months ago

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Augustiner, Not sure if you are referring to an install we have done, one of our houses in Brooklyn, or our house in South Jersey? The heat pump heat I removed was in NJ with 2X6 walls and blown in insuation. The heat pump drove a Unico high velocity system. The Unico is good for cooling, but heat pump heat is a disappointment. Insulation is always good, assuming you have stopped all infiltration. Nevertheless, I couldn’t recommend heat pump heating North of Virginia. When you need it the most, it is least efficient. Zoned hydronic heating is the most comfortable and efficient, not strictly from a boiler efficiency (as most brownstones are limited to 83-85% mid-efficiency boilers), but from a granular ability to only heat areas that you specifically want heated.

Augustiner | 12 years and 4 months ago

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Hey Brucef, I am very interested:
how much BTU did you have per floor, and how is your house insulated?

ellenlourie | 12 years and 4 months ago

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You still need heating system. those units rated for 47F outdoor temperaature , and will decrease heating output with outdoor temperature falling. so you will have least heat when you need most.

brucef | 12 years and 4 months ago

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As Zarathustra spake, link still looked like electric resistive heat.

Erstwhile | 12 years and 4 months ago

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Looks like electric resistance heat.  Not the way I’d go.  I know you said you are set on this system, but if you are looking to limit yourself to one system for heating and cooling you would be better served with a hydronic fan coil system like those from Unico/SpacePak or Multiaqua.

brucef | 12 years and 4 months ago

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Is the Mr. Slim you are considering a heat pump with maybe electric supplement?   You will not be happy with heat pump performance in this climate zone. Shoulder seasons are Ok, but winter is inadequate no matter what the sales pitch says. Electric resistant supplement is expensive, bad idea. Even in shoulder season, I removed the heat pump I installedin my home. The heated air that the heat pump produces is technically warm. The evaporator warms the air, but it feels cool to your hand. There is no comparison to the warmth given off by a hydronic radiator.

karenanne9 | 12 years and 4 months ago

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Thanks for your comments and good luck!  Appreciate the link to Brooklyn Insulation as well. Unfortunately, money is an issue.

Augustiner | 12 years and 4 months ago

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I stood in a building with fresh spray foam for 2 weeks and felt sick. I wouldn´t want to live in that. What I am doing:
stone wool on the front interior, attic under roof and between cellar and basement.
4 inch polyiso on exterior back wall. New tilt&turn windows. You can also do cellulose on interior (check http://www.brooklyninsulation.com/)
City Multi conceiled multi-split units with small ducting on 5 floors, for heat and AC.
I take the risk – I will have no heating backup. Generally speaking I like hydronic radiators, they are for sure better than forced air, and probably also better than using a ductless split system. So if money is not an issue, then go for it.
If you do all new installation I´d go for radiant floor heating.
By the way:
Your office radiator is probably 50 years old without a temperature valve and is surely not the kind of system that you would use in your apartment. Only because energy prices are still to low, some people in NYC turn on the AC in winter to cool an overheated room (it´s true)

karenanne9 | 12 years and 4 months ago

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Thank you.  So what would you recommend?

jigman | 12 years and 4 months ago

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You cannot use closed cell foam spray insulation unless you install an outside air exchanger to exchange stale/moist air with fresh air.  This kind of spray insulation makes your building extremely air tight, which is good, but not if you cannot get out unwanted moisture.  You could end up with mold problems in the future. Good luck.