Heating & Cooling

"Can we have multiple heating zones with this setup?"

What far reaching affects this innocent question had! Our original plans for an HVAC system were fairly typical for a new home in the US: single-zone, central-air, powered by an efficient gas furnace with an attachment point for a future air conditioner coil. You can add zones to variants of this system, but it becomes increasingly complicated (and expensive). Yuval suggested that we look at heat pumps.

What is a heat pump?

A heat pump uses condensation and evaporation of a refrigerant to heat or cool a space. Air source heat pumps use the air as the energy source/sink. It doesn't take much to get a feel for how heat pumps can heat a space:

• Evaporating the refrigerant transfers energy from the air into the refrigerant. The loss of energy leaves the air cooler.
• Condensing the refrigerant transfers energy from the refrigerant into the air. The addition of energy leaves the air warmer.

This may make it seem like heat pumps would require the space where the energy is coming from to be warmer than the space where the energy is going to, but this isn't the case. The heat source only needs to be warm enough to transfer energy to the refrigerant, and the heat sink only needs to be cool enough to accept heat from the refrigerant.

Refrigerators and freezers illustrate this well. They use a small air source heat pump to make cool spaces even cooler by transferring the energy in the fridge into your kitchen (which is, hopefully, much warmer than the fridge or freezer).

For further details, you can read this article and these not-very-good Wikipedia articles: Heat Pumps, Air Source Heat Pumps. And at this point, my facts become an amalgamation of things I have read and things I have learned in conversation — sorry about the lack of citations.

Some trade-offs

Heat pumps are fairly rare in the US today. They are more common internationally (the system we are going with is from Mitsubishi), and the systems have been around for a while. They are common enough, and becoming more popular as their efficiency is recognized, that we shouldn't have problems maintaining our system, but it is a risk.

Heat pumps, at least the ones we are considering, are driven electrically, but run at a much higher efficiency than electric baseboard heat. They are more comparable to an efficient gas furnace, but as the opening question points toward, heat pump systems are easier to configure into zones. Separately-controlled and conditioned zones are often more efficient since you aren't heating the whole house to the same level, but just the area(s) you are currently using. The Mitsubishi system provides a number of other efficiency features, such as providing a variable amount of conditioning (instead of full-on or full-off), and less heat loss in the small, well-insulated refrigerant lines versus standard ductwork.

Heat pumps require refrigerant, and refrigerants are a negative, as far as the environment is concerned. This is partially mitigated by fact that this is a long lifetime, closed system. Mitsubishi also uses refrigerant that has a low environmental impact.

Some heat pump systems, including the one we are using, are reversible — they can transfer energy in  and act as a heater or transfer energy out and act as an air conditioner. Even though we were not planning on installing an air conditioning unit at construction time, using a system which supports both functions results in a simpler, more cost efficient solution.

No ducts! The refrigerant line is hardly larger
than the wiring, and with the wrapping
it's still ~2" in diameter

Heat pumps have one more really big advantage for a green home: they don't require ducts. We are going with a fully ductless setup where the refrigerant lines run directly from the exterior units to the distribution units. This allowed us to open up the main floor by removing the need for some interior soffits. The impact on the roof was much more substantial. Because we don't need to run ducts, our home is now able to support a roof design that provides a significantly higher level of insulation. Since the roof is one of the large energy leakers in a standard home, this will result in a much tighter home. (Sneak preview: this ended up having some unintended consequences in our kitchen.)

Our system

We are going with a Mitsubishi heat pump system. Two external heat pump units will drive six interior distribution units, for a total of six different zones (one per bedroom, two on the main floor, and one downstairs). We decided not to go with programmable thermostats since they are expensive and the units we are buying support a basic level of programmability — a single day/night cycle — that is good enough for us.

Not ugly, but not exactly beautiful

This is one of the units (installed over the door of our dressing room). The units are not huge, but they are not small either. Each unit is about the width of a doorway, and about a foot tall and a foot deep. This is fine in the bedrooms and media room, where we were able to put them in fairly out-of-the-way locations (over doorways). However, we were not able to do this in the open living area of the main floor; we put the distribution unit behind the fireplace — okay, but not ideal.

This was actually a bit of a disappointment. We initially planned to do a system that used small ducts on the main floor to move the air from the distribution units to the open space. This is when green politics got involved. We're going for a Built Green certification on our home — this is a nice-to-have that gives us a verification that our home is green by some external standard and is also good marketing fodder for our builder. To get a Built Greet certification, your heating system must be Energy Star approved. However, Energy Star does not handle configurable systems well.

The exterior hookup.
The installed unit will only be 3' x 3' with a depth of 1'

Both the ducted and ductless variants of the Mitsubishi are Energy Star approved. However, what is not approved is having a single exterior unit drive one ducted interior unit and one non-ducted interior unit. Energy Star approval applies only to the exact system that was evaluated. This makes sense — variations could potentially decrease the efficiency of a system. However, approval is binary, and there is no process for getting small variants approved; the variant has to go through the full approval process, and the cost of that is prohibitive for one-offs or all possible combinations. Okay, rant over =)

Overall, we're happy with the configuration that was installed. We'll provide an update once we've moved in and have experienced how this works in practice!

Review of Q1 2012

The first quarter of 2012 is over, and it was a quarter of great progress. It was the quarter of rough-in work.

Framing was completed:


Plumbing was added:


Then HVAC:


Fireplace:


And electrical:


Windows were installed:


And then siding:


The timelapse for the quarter shows all the exterior pieces coming together.


We spent a lot of time on design this quarter. Some of it was just-in-time design, such as the electrical and lighting. Framing changes were made based on 3D models of the interior. The master bath won't be installed for awhile, but the tiles need to be ordered now. There was a steady stream of small decisions, such as the fascia color for the roof trim. Many design discussions are ongoing as we take our high level design ideas and then refine the details as we gather samples, compare colors, and work through every individual piece.

The rough-in work is nearly done, and we are anxiously awaiting insulation and drywall. These will mark the beginning of the finish phase of the project. Each successive stage will appear to move at a slower pace, as more care is taken to perfect the details. Several areas may be in-progress at the same time, though. To accommodate this change, we will replace our weekly summaries with weekly overviews focusing on a single area. We'll go into details on individual elements, providing more background and design information, plus in-progress and final pictures of the installation. Our photo gallery and timelapse gallery will still be updated regularly with each weeks' progress.

Dirt-moving and Inspections

Not a lot of interior work was done last week. Rough-in is nearly finished, so time on site was filled by inspections and corrections. Outside, more siding was added, the decks are closer to being finished, and dirt moving for landscaping was started.

More electrical work was done — in theory, but not in practice, the last of it. The electrical panel was labeled, and the connection to the main service is nearly ready to go. We asked for a small correction in the media room, and a larger circuit put in for the kitchen for an electric-powered stove. Temporary circuits need to be added for space heaters to dry out the interior before drywall. This will all happen this week. However, the electrical inspection was approved, along with most other rough-in inspections. Mechanical required a small correction around the fireplace, but everything else that was ready has been approved. The only remaining inspection is for framing, which requires some work from the insulation installer this week.



More siding was installed on last week, including the lower south side, the north side of the garage, paneling around the stair tower door, and some paneling around the living room windows.



Nicer weather provided an opportunity for more progress on the deck. The living room deck was evened out, sanded, and is now ready for the finishing stain. The upper deck was completely finished, including staining. The wood has darkened and is a richer color now. The finish looks uneven in the picture because it was still drying.



The most important work last week was dirt-moving. The entry-way was filled in with dirt and can now serve it's stated purpose of letting people enter. The driveway was smoothed out, so it can now support a concrete truck pouring the slab for the garage floor. The front yard in general has been leveled, and prepped for hardscape and landscape. The area between our house and the neighbor's is being prepped for landscaping (which has been designed). Finally, our backyard has been smoothed.



The camera wasn't pointed quite low enough to capture the dirt being moved, but you can see the movement of the excavator. The end of the week shows the finishing work being done on the rooftop deck.



Poplar has been delivered for the windowsills, which will go in soon (before the drywall). Fire breaks (to keep fire from spreading in the walls) need to be put in this week, then the framing inspection can happen. Now that the entry has been filled in with dirt, the entrance through the garage can be sealed up, and a blower can be put on the front door to find and seal any leaks in the envelope of the house.

Siding and Wiring Conduits

Last week mostly saw work on the exterior siding for the house. The electrician came by for just a bit to work on some of the last details. However, a few more questions came up, so the electrical work wasn't quite finished last week.

Quite a bit of the lap siding was installed, including the north side, upper level on the east side, the north-west side, the upper south-west side, and the upper south side.



We acquired the exterior wall washer light we're going to use on the west side of the house at night. We tested it out one evening after dark, and it should do a good job highlighting our house.



The last major piece of wiring (I believe) was getting conduit for future cabling run. The endpoints are in the living room, kitchen, office, master dressing, and second bedrooms. These run down into the crawlspace, except for the office, which runs directly into the server closet. The server closet then has a single conduit that runs into the crawlspace. The media room has a conduit that runs from the closet up to the projector mount to send video up there.



I spent some time exploring the crawlspaces under our house. The crawlspace is quite generous, and there are plenty of pipes, ducts, and wires running under there. The space is large enough that we added some stub points for lights. Under the garage you can follow the electrical wiring back to the central electrical panel.



The timelapse shows the siding installation (the work later in the week was covered by a blue tarp to protect from the rain). You can catch a brief glimpse of snow falling Tuesday morning.



Next should see more work on the siding. We are hoping to have the inspections finished up soon; maybe this week if we are lucky.

Electrical Wiring, Exterior Finishing

This week saw more good progress on both the interior and exterior. The electrical wiring is nearly complete. Some exterior finishes, including siding, exterior soffits, and the rear deck all saw work done on them.

For electrical wiring, the interior line voltage work (lights, switches, electrical outlets, and a big, beefy cable for an electric car charger in the garage) is nearly completed. There might still be a few details left, but not much at all. The majority of the data wiring was completed, with Ethernet, cable, phone, and low-voltage for security or home automation run throughout the house, and speaker wire plus a bit of subwoofer coax cable run in the media room. There is still some wire that needs to be run for exterior lighting and electrical outlets, and then a few conduits for future data wiring and media room wiring need to be run. Those should be complete within a few days, and then the electrical inspection can be done.



The fireplace and gas connection on the back deck were installed this last week. The fireplace has been mostly covered up to protect it, but since part of the cardboard was detached, we took the opportunity to get a picture of it.



Some ductwork for the HRV unit was added.

Some of the exterior finish work was started last week, too. The HardiePlank and HardiePanel siding was delivered Monday morning. The panels were put up on the stair tower during the week.



It is not painted, and there may be some other details in the channels between the boards to do, but it is starting to give a feel for what the finished house will look like. The HardiePanel is being used for the lower exterior soffit, and the bit of that was installed. The upper exterior soffit was installed using a knotty cedar.



The flooring of the back deck was laid down on Friday. It isn't fully finished, but looks quite nice already, especially when it gets wet.



We finally moved the camera to a position right in front of the house. It should be able to capture all the upcoming work on the entryway, siding installation, along with all the general activity of people moving around during the day.



Next week should see electrical finished, and some inspections done. Once all the rough-in inspections are done, insulation can go in; but we don't expect that to happen this coming week. Siding and/or deck work will probably continue on the exterior. The next big piece outside will be getting the entry foundation backfilled and the driveway filled in for better support. Once you can actually walk in through the front door, the missing panel in the garage will be filled in, and the house can be sealed up and tested for leaks. Then the garage can be cleared out, and the cement slab poured in there, which will allow installation of the hot water heater. We're not quite sure on the timing of all that, though, because a bit of landscape design needs to be done on the north side of our house (south side of the neighbor's), so that all the dirt-moving can be done at once.

Lights and a Deck

This was another exciting week of work on the house. Electrical was started, including a lot of the lighting layout; and the rooftop deck was framed and finished.

Electrical wiring was started on Monday, and a lot of progress was made. One of the first steps was placing all the can lights so we could approve the positions before they were wired. We're using 6" cans in most of the house, and 4" cans upstairs (they have better sealing than the larger ones, so they won't lose as much heat through the roof) and in a few places downstairs that we want to highlight. The electrician started placing mount points for lights such as pendants and sconces, electrical outlet boxes, light switch boxes, and tying it all to the central electrical panel.



On the exterior, the deck part of our rooftop deck was built this week. The frame for the bench and under-floor was put together earlier in the week, and then the batu planks were put in place at the end of the week. There's probably still some finishing (sanding, weatherproofing/oil/sealant of some manner), but it already looks really good!



The timelapse video has a few interesting points: first the bench frame above the garage goes up, then the garage window followed by the master dressing windows are installed (the final windows in the house), and then the batu planks on the deck wrap around the bench.



The monthly summary shows the vapor shield and foam being installed, along with the windows and upstairs doors.



More wiring will be happening next week, maybe including data wiring. The fireplace was delivered, and the space has been prepped for it, so that install should happen soon (it has to be installed before the gas inspection can happen). The knotty cedar for the exterior roof soffit was delivered. The rest of the siding should be delivered soon.

Master Bath Design

Last month, we refined the design of the master bathroom. While we had the counter, cabinets, tiles, sinks and other plumbing fixtures picked out, we hadn't discussed the mirror or light fixtures, nor had we detailed the tile layout or the placement of the glass wall and bench in the shower.

Vanity

Yuval proposed an initial design that we mostly liked. It had separate mirrors raised out from the wall, with some open shelving backed by an illuminated panel between the mirrors.

He gave us a second draft which coordinated better with our shower tiles: FAP Amour Mer accent tiles paired with FAP Fusion White tiles. The Fusion White tiles have a subtle gradient texture which makes them more interesting than plain white. Yuval proposed using the Fusion white tiles for the backsplash and all the way up the cabinet wall. This was a big change from the organic pebbles in the original design, but we liked it.

Shower

We want a fixed glass partition in the shower so that we don't have to deal with a door. But which side should have the opening? With the shower head on the west wall, an opening on the east was the natural choice (and would minimize escaping spray). However, the deck door requires a step that would overlap with the shower entrance. It also makes sense to put a shower bench opposite the shower head. To accommodate these constraints, we decided to anchor the shower partition to the east wall and put the opening on the west, by the shower head.

What's next?

This design was enough to get the tiles ordered, and allow lighting to be placed. The rest of the decisions can wait until closer to when they are needed. There is still plenty left to do: finalize the the mirrors and the shelf, choose wood for the bench by the cabinets, choose the treatment for the glass partition, figure out shelving in the shower, and place and choose hooks and towel bars.