Things are starting to take shape at ‘The Barn’! The house is fully framed and sealed up, and now plumbing, heating, and electrical are being installed. It’s been a ‘fun’ experience managing the install of these systems*, and I’ve learned a lot.
So here’s a round up of what we installed and some lessons learned.
*We have very skilled professionals doing the install, but I’m the general contractor on this project, which is something I’ve never done before, and something I’ll never do again. I’ll write a blog post on that experience when it’s over
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House Stats
This information is helpful when determining your heating and insulation needs. Make sure you know your climate zone 🙂
Location: New Hampshire
Climate Zone: 6
Size - Exterior Dimensions: 24’ x 32’
Size - Interior Gross Square footage:
Basement: 713 SF
First floor area: 713 SF
Second floor area: 713 SF
Design goals:
- Air tightness: Less than 1 ACH
- All-electric house (no fossil fuels)
- Plastic and foam free to the greatest extent possible
Floor Plans
BASEMENT PLAN
FIRST FLOOR PLAN
SECOND FLOOR PLAN
What it should look like when complete.
Heating
This is a heat pump wall unit.
We are heating our house almost entirely with air source heat pumps (mini splits). These are the unducted variety, the kind with the not-so-attractive wall units. But I’m taking efficiency and cost over aesthetics here.
Heat pumps are really energy efficient, and they can extract heat out of the air even when it’s below zero degrees. Of course, in our climate we need to make sure we’re installing ones that are designed for cold climates.
We won’t be installing any backup heat in the areas that we have the heat pumps since they work efficiently at such low temperatures.
Locations:
The house is pretty small, and the first floor is pretty open. So we’re only installing one wall mounted unit on the first floor.
The second floor of the house has 3 bedrooms, a bathroom, and an open office area. We’re putting a wall unit in the open office area and in one of the bedrooms (my bedroom). The hope is that the unit in the open area will heat the kids' rooms as long as they keep their doors open at night.
We decided to not put any heat in the basement. This is just a storage area and our workout space, so it’s fine (and much appreciated when working out) if it’s cooler down there.
The image below shows the wall unit heat pump location for the first floor. It's the black box and wires in front of the stairs.
Auxiliary Heat:
I think the mudroom area of the first floor won’t get tons of heat gain from the heat pump unit, so we’re adding an electric radiant heat mat under the tile floor. This type of heating is not very efficient, so we’ll only use it when truly needed. It’s more of a ‘just in case’ installation if we find that the mudroom is constantly cold.
The upstairs bathroom will also have electric radiant in the floor. But this will probably be used regularly because I can only sacrifice so much comfort.
And we’re going to install a small electric wall heater in the kids’ rooms. This will also be a ‘just in case’ heat source if we find that their rooms don’t get warm enough with the hallway heat pump unit.
Cooling
Besides efficiency, the best thing about heat pumps is that they provide both heating AND cooling. So we don’t need to add any extra equipment to cool the house in the summer.
We’ll also have a ceiling fan in the living room, and all bedrooms and living spaces are set up for cross ventilation. (I talk about that more in this blog post.)
Mechanical Ventilation
All homes should have balanced mechanical ventilation, but an air tight house MUST have a whole house balanced mechanical ventilation system. This provides fresh air and removes moisture.
We’re installing a ducted Panasonic InteliBalance ERV (Energy Recovery Ventilator). These units help save energy by preheating the air coming into the home with the stale air that’s being exhausted. They don’t physically mix, but they pass by each other, sharing their heat. In the summer, the opposite occurs - the cool, outgoing air will extract heat from the hot, incoming air before it reaches the rooms.
Lesson Learned:
Open Web Floor Trusses Make Things Easier:
Here's the kitchen ceiling we had to drop down to provide room for the ERV ductwork and the larger plumbing runs.
This is the first time I’ve installed a ducted ERV in a home that wasn’t framed with floor trusses, and it was a pain! Our floor framing is 2x10 lumber.
We ended up having to drop the kitchen ceiling to get the ducts and plumbing to the second floor. Luckily we have 9’ high ceilings on the first floor, so dropping the kitchen ceiling by 1’ wasn’t a terrible thing. But it would have been nicer if we had open web floor trusses so all the ducts and plumbing could be within the floor framing.
Ductwork, whether it’s a heating / cooling system or a ventilation system, cannot go in unconditioned spaces. So we couldn’t run the ductwork in our attic since it’s an unconditioned space (it's outside the building envelope).
Provide A Chase:
This is the chase we made for the ERV and plumbing runs.
It’s also a good thing to provide a chase, which is a vertical opening (imagine an elevator shaft) that goes from floor to floor. It’s a helpful way to get plumbing and ductwork to different levels of the house.
I didn’t have a chase designed into the floor plan originally, so we had to find space for it after the fact. We had to take the space out of the entryway closet, which was a bummer.
Plumbing
A small house makes it easy to keep plumbing runs short and compact.
To help keep plumbing costs down and heat loss in water down even more, I grouped all the plumbing together, and stacked the second floor bathroom directly above the first floor plumbing areas.
The red circled areas show the plumbing locations.
- All plumbing is on the west side of the house.
- The water heater in the basement is below the kitchen.
- The first floor powder and kitchen are side by side, directly above the basement water heater.
- The second floor bathroom is directly above the kitchen.
We used pex for our water lines. I tried finding a healthier solution, but plumbing seems to be a really hard place to avoid potential toxins. An alternative would be copper, but as we know, copper is incredibly expensive. And it just wasn’t feasible for our project. We’ll monitor our water quality regularly.
The waste lines are PVC. This is the one place where I don’t have a better alternative for using plastic.
Electrical
We kept the lighting in the house pretty basic. We’re doing recessed downlights for most areas of the first floor. These will be integrated LED fixtures, meaning you can’t change the light bulb when it burns out. You need to replace the whole fixture. But that shouldn't be for 50 years.
You can set the color temperature of the light before you install it. I think we’ll set ours at 3000K. This gives enough light for seeing comfortably but it isn’t super bright task lighting.
To avoid penetrating the attic Intello Plus membrane air barrier, the second floor was designed to not include any recessed lighting. We’re doing wall sconces in each room instead.
We strapped the second floor ceiling with 2x4’s to provide a larger service cavity for the smoke detectors that would be installed on the ceiling. The 2x4’s would give enough room between the air barrier and the drywall ceiling to install the smoke detector without cutting through the air barrier.
Lessons Learned:
The 2x4 strapping stops at each wall top plate, so electrical wires can't run from room to room.
The 2x4 strapping ended up not being an effective service cavity for the electricians because the strapping dies at the top plate of the walls of each room, so there’s no way to run the wires from one room to the next.
What we should have done is installed the strapping before building the interior walls. That way the strapping would have been continuous across the whole ceiling, and the electrical wires could run from room to room.
Turns out, the 2x4 strapping created a big enough cavity for recessed lighting. In all my efforts to avoid recessed lighting in the second floor ceiling, it was in vain. The LED fixtures are narrow enough to fit into the 2x4 ceiling cavity. So I could have installed recessed lights in all of the upstairs bedrooms rather than installing wall sconces. Recessed lights are much cheaper.
Outlets:
Since we aren’t installing exterior insulation on this house, the insulation in our wall cavity is very important. Outlets installed on exterior walls decrease the amount of insulation. So every outlet we have on an exterior wall will be a bit of a cold spot.
This made it very important to minimize the amount of outlets we installed on the exterior walls. I tried my best to shift as many outlets and light switches to interior walls as possible, but since code dictates outlet spacing, it’s impossible to completely avoid outlets on exterior walls.
Lessons Learned:
In the past, I’ve been hesitant about providing electrical service cavities in exterior walls. A service cavity is basically an additional wall that you’re building inboard of the exterior wall. This service cavity allows you to run all your wiring and install all your outlets without cutting into the exterior wall and diminishing the amount of insulation in the wall cavity.
I’ve been hesitant about them because of the cost it would add to a project to have to build out the additional wall. It also reduces the usable square footage of the house since it grabs about 3” around the entire perimeter of the house. That's 6" total in length and width. In a small house, those inches matter!
I now wish I had done them on ‘the barn’. And I’m more apt to design them into future client homes as well. I’ll be less likely to do so if the house has continuous exterior insulation, but if it’s a double stud wall system or a single stud wall like our house, then it would make a lot of sense.
The service cavity is also very helpful if your air barrier is on the interior side of your exterior wall. but in our case, we used the exterior side of the wall as the air barrier. (Learn more about air barriers here.)
This is a section through what the service cavity would look like. Image: 475.supply
Example of service cavity. Image: 475.supply
Final Thoughts
Once electrical and plumbing rough-ins are done, we can insulate and drywall! Then it’s just the finishing touches (that take a lot of time.) We're hoping to be done in about 1.5 months.
Coming up: I'll be doing an Insulation post to talk about what we're using and how the install has gone and an Air Barrier post to show where we put our air barrier and the ways we're keeping our house super air tight. Stay tuned!