The Cape House Guide to Heat Pumps
Layouts, design tradeoffs, and equipment selection for the iconic MA style
Guys, this is literally ARTHUR’S HOUSE:
Much like how triple deckers are iconic in Cambridge, Somerville, & Boston, the Cape Cod house is an iconic style throughout Massachusetts.
I mean, it’s literally named after Cape Cod. Can you find any other home style that shares its name with a lineup of chips?
Read on to find out how we install heat pumps here.
This is the third entry in our Boston metro architecture series. Here are the other 2.
The Summary
Cape houses make up ~20% of all Laminar Collective signups. Since they don’t really have attics, this makes them easier to design.
You basically have 2 options:
Ductless units in every room
Ductless units upstairs + ductwork downstairs from the basement
What makes design just a bit more difficult is that:
Rooms on the 1st floor tend to be small, and may have limited wall space
Floor plans can be fairly closed, which means that you can’t cover the entire 1st floor with 2 mini-splits, like a colonial
If you have 6 or 7 zones to cover, ductless w/a single outdoor unit = oversized1
The proper solution is to go for 2 outdoor units with low min. capacities
Or to consider basement ductwork
In general, due to the downsides of ductwork in the basement (e.g. lower performance, and more points of failure w/ducted systems in general), we recommend going with a ductless setup unless you have to go ducted for the 1st floor.
Let’s go over the layouts, and the exceptions we’d consider for basement ductwork.
Standard Layouts
Since every cape has 1 or 2 bedroom on the top floor, the big difference in layouts is on the 1st floor. There, we typically see 2 configurations:
Linear
Boxy
Linear floor plans feature a living room, dining room, and kitchen all in a row, with maybe 1 or 2 bedrooms on the other side.
Boxy floor plans tend to have more open spaces.
I find that the linear floor plan is slightly harder to design for, because you need to place a mini-split on either the front or back walls to fully blow into that open dining room.
However, this is difficult b/c some people don’t want exterior line set on the front of the house, and the kitchen is usually really cluttered with limited wall space:
Whereas with the boxy floor plan, it becomes easier to tack a mini-split on the side walls of the bedroom & living room.
Got your floor plan in mind? I want you to count how many 1st floor zones you have: this is every discrete open space. Keep that in mind, because it will directly inform our design choices.
Design Considerations
Behold, a scenario chart:
Ductwork typically has an advantage over ductless if you have many small rooms clustered together, either directly above or below a large, unfinished space.
If you have 4 zones on the 1st floor, go ductless by default
If you have 5 zones or more on 1st floor, then maybe consider ducted
But the question is whether that advantage supersedes the known disadvantages (e.g. more points of failure, costly materials, it takes up space!) of basement ductwork.
I’d say that it may reach that point if:
There’s no good wall space for a ductless mini-split or a floor unit to go on
You don’t have enough panel space for 2 outdoor units (4 breaker slots)
Note: ducted 2nd floor is not something we do. No attic + only 2 zones max.
Exterior
For the both floors, you may need to access multiple entry points for the refrigerant lines on various external-facing sides of the house. To do this, you’ll likely need to run lines across the basement, or into the basement & up through the ceiling.
For the 2nd floor bedrooms, particular, you have to access them through the side of the house since you can’t punch a hole in through the roof. That’d lead to water problems.
So, long story short: expect refrigerant lines running up the side of the house, and into/through the basement.
Sizing & Equipment Selection
Cape houses usually aren’t massive. Manual J heat load calcs typically don’t exceed 35,000 BTU, which is the capacity of a standard 3-ton outdoor unit.
Therefore, if you go ductless, I’d recommend 1 outdoor unit for 5 zones or less, and 2 outdoor units for 6 and above. With 2 outdoor units, you can turn off 1 outdoor unit during the shoulder season, when the heating/cooling load is lower.
If you go mixed ducted, I would consider standard ductless units on the 2nd floor, and a well-sized medium-static air handler for the 1st floor.
These slim fit/pancake models have lower capacity than the high-static (read: stronger fan) models, but are flat & easier to suspend from the top of an attic.
We’ve confirmed with a temperature gun that the 1st floor does, in fact, get pretty cool with this configuration:
Since the ductwork isn’t in a hot, stuffy attic, the discharge temp is pretty good. In the same Arlington installation as the video, a Daikin FDMQ air handler registers 52°F discharge outside of the supply, cooling the 1st floor to 70°F on a 86°F day.
Installation Process
Installation will typically take about 2 to 4 days. (We’ll add photos soon!)
Ductless (2 to 3 Days)
Day 1 - Supply run & kickoff. Mini-splits are mounted on the walls. Line cover starts going up. Refrigerant lines are run, and cover may/may not be completely on by the end of the day. Condenser is mounted on pad & stand.
Day 2 - Electrical work is complete, outdoor unit commissioned after passing pressure & vacuum tests. Line covers fully on.
Day 3 - Half day buffer period (e.g. weather, logistics)
Mixed Ducted + Ductless (3 to 4 Days)
Day 1 - Supply run. Ductwork trunk fabrication. Basement work, registers are cut. Air handler suspended.
Day 2 - Connect ductwork. Hang mini-splits. Run refrigerant lines. Condensate pump for basement air handler. Outdoor unit set in place.
Day 3 - Electrical work. Outdoor unit commissioned after passing pressure & vacuum tests. Line covers fully on.
Day 4 - full day buffer period.
Market Pricing and Cost Breakdown
Market prices are going to vary wildly, as they always do. I can tell you how we approach pricing, though:
~45% equipment + materials
~27% labor
~27% overhead
Here are the pre-rebate prices. Ductless is pretty simple:
Here’s the breakdown for that, with a 6-zone example:
With mixed:
Breakdown:
Simply put, ducted installations are more complex than ductless. And that’s why it justifies a higher labor rate.
Rebates
Going to copy this section here from my triple decker article..
Mass Save offers a $3,000/ton rebate per unit, maxing out at $10,000.
If you have 1 outdoor unit, probably ~$9,000 ($3,000 x 3 tons). If you have 2 outdoor units, you’d probably get the full $10,000 rebate.
There’s also the federal tax credit of $2,000, but it’ll be gone by the end of the year!
Conclusion
Finally. I’m 3/4 of my way through with my Boston architecture series. Only the white whale of Somerville 2-families (upper units) remain.
I’m visiting all the small towns in MA. I’m meeting locals where they are. (You. You’re the local!)
When I first started, I told some friends that this was going to be the Bourdanian period of my life where I spend like 3 or 4 years exploring & writing about some industry and all the unique quirks of it. While, of course, trying to tackle climate change & get people efficient cooling + heating at an affordable price.
With this article, we are getting closer to all 4 articles in the series!!
I’d like to thank Jing Pan specifically for helping with the outlining & research, and to the lovely Jillian Wilson-Martin in Natick for bringing to my attention that Natick has a lot of cape houses! It’s a beautiful town. I hope some of you reading this live there & find this helpful.
Why? B/c the more indoor units you connect to an outdoor unit, the higher capacity the outdoor unit has to be. Manufacturers don’t make low-capacity + high # indoor head units (yet), and there’s an argument they shouldn’t b/c the market size (small homes with a lot of rooms) is rather small
We have seen lockup using our several year-old single Mitsubishi condenser set to Auto Mode when one mini split asks for heat and another for Cool in the shoulder seasons. This is why we’ve gone to 1 Condenser per mini split. Is this still the case with newer condensers? https://copilot.microsoft.com/shares/bvK6grwbPo1vV8x8uFb5T
What about side-by-side townhouses (or townhouses in general)? They are a little less common than some of the ones you listed, but anyplace with housing built after 1970 has them. (Arlington, Medford, Cambridge, Quincy, etc.)