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Mechanical equipment that is tuned to the space it must condition: a small air handler and ceiling-mounted mini-splits
So, heating and cooling systems. This house has a boiler which means that we’ve got radiators throughout the house that are providing really great heat.
We’ve got in-floor, we’ve got standard cast iron all over. But cooling is something that these old houses didn’t come with. Now upstairs in the attic, where we foamed the whole lid and made this whole thing super super super tight, we were able to put in an air handler and what we might think of as a traditional forced-air cooling system that’s providing cooling to the second floor.
Very short duct runs, easy to do, easy to balance. And because our BTU load overall went down, we’re able to put a fairly small air handler from Mitsubishi up there.
Now when it comes to the first floor, we don’t really have a great way to bring enough ductwork down to the first floor to provide cooling.
Moreover, I don’t particularly like ductwork. It usually gets pretty gross in there, people don’t clean it as often as they should, and so the other way to bring cooling into a house is with mini-splits.
But when you say mini-splits, oftentimes people’s first reaction is kind of like ugh. They don’t like the wall wart, they don’t like the thing that sits on the wall.
And Mitsubishi came up with a really, really brilliant system for us to bring mini-split cooling into a space without having the thing on the wall that people object to. It’s actually right above me. In the ceiling, we have a ceiling cassette. Now this is a traditional mini-split, in the way that we would normally think of it.
Except that the only thing that we’re going to see is a white grill on the ceiling like a ceiling fan or something else. Other benefit of putting it here in the kitchen is I’m got some south facing and I’ve got some west facing glass, so this is going to be a really warm space.
And it’s, in terms of comfort, how the person reacts to the space, this is going to provide cooling where we need it and want it most."
Mini-split air-source heat pumps can provide heating or cooling where it’s needed, rather than where it’s needed as well as where it’s not needed.
In the kitchen, a ceiling-mounted unit provides cooling, and in the renovated basement another one provides heating and cooling. The hyper heat technology of Mitsubishi mini-splits means they work well in very cold climates like Minneapolis.
Encapsulate the attic with spray polyurethane foam
An air handler in the attic provides cool air to the upstairs of the house. 100 years ago when the house was built, very little insulation was used.
Even when they did begin insulating attics, it was in the attic floor and it was usually inadequate. Air conditioning equipment that was added in the 80s and 90s was added above the insulation, putting the AC unit outside the house.
To tighten the shell and to place the mechanical equipment inside the thermal envelope of the house, we’re going to use spray foam on the underside of the roof deck.
The attic is the hottest part of the house during summer, so it's critical to get the air handler out of the heat and into the house. Downstairs, the Mitsubishi units are great for remodeling because they slip between 16-inch on-center framing, which happens to be the way this house was built.
The cover plate is left off until the drywall goes up, so the guts of the unit are protected with a temporary cover.
Refrigerant and condensate lines from inside the unit can snake through the framing through ceilings, walls, and floors on their way outside to the outside compressor unit, where excess warm or cool air is dumped.
We’re going to put R-50 on the roofline, we’re going to bring all the ductwork and the mechanicals inside the conditioned space, get a new air handler up here that’ll be tied to condenser that’s also running a couple of our mini-splits below.
Another tricky space in the house is the sunroom. It’s heated with a classic radiator, which will be fed by a high-efficiency boiler, and these single-pane windows will be replaced with energy-efficient windows.
But even with a low solar heat gain coefficient, this room is likely to need cooling in order to live up to its full potential.
So we’re going to put one of Mitsubishi’s EZ Fit ceiling cassettes into the ceiling, running the condensate and refrigerated lines down the wall, across the floor system, and out the house to the condenser unit.
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