Construction Update 2
Things have been happening at a fairly rapid pace for the past few weeks.
- Both the plumbing and electric rough in's have been completed, and inspected.
- Our electric meter was installed by the Utility.
- Insulation of the outer wall assembly is complete
- The Zehnder Ventilation system has been installed (except for the ducting to the outside)
- The air source heat pumps have been installed.
So lets take a closer look at the plumbing system:
We have incorporated a few different components not very common in our area.
Drain Water Heat Exchanger
This is a slick little device. It looks like a big copper tube. From an engineering perspective, the fewer moving parts the better! Moving parts break or need maintenance. In a Passive House the largest energy load is heating hot water. The drain water heat recovery component simply takes the warm water going down the drain and "pre-heats" the cold water going to the shower valve as well as the cold water entering the water tank. The efficiency of this component is directly related to length. In our case, we are using a 48" long heat exchanger. This will recover roughly 50% of the heat going down the drain.
Hot Water Circulating Loop
We decided to utilize a hot water recirculating pump for a few reasons.
1) We have a raised fill septic system and with a recirc pump we will save thousands of gallons of water per year and put less stress on our septic system.
2) Hot water will be the largest single energy user in our house. When you open the hot tap, the ambient water leaves the tap and goes down the drain. The water heater tank then begins to feed the hot water into the system. The tank is then filled with cold water from the street. It is then heating that water from 50 degrees (or less) to the desired temperature. With a recirc we will just be reheating the ambient water in the loop (70 degrees or so). This is a huge savings in energy!
Check out how the system works here:
Both of these items require us to insulate the hot / tempered water pipes. The insulation will only make these systems work better.
Hose bibs are something I wish I had given more though earlier in the process. Probably the best thing would have been to do Yard Hydrants, since they exit the house underground, the thermal bridge impact is much less. The Rim Joist insulation is 24" deep. we decided to go with a 14" hose bib connected to Pex with a shutoff valve inside the basement. The Pex is much less conductive than the copper, but also ensures the hose bib copper shutoff should never get to the freezing point.
Not much is different on the electric side of things. In an effort to minimize the electrical penetration to the outside we decided to install a sub panel in the Garage to power all of the exterior lighting. The only other electrical penetrations are from interior switches to exterior lights. Those holes were sealed using special wire gaskets from 475. This made air sealing the wires very fast and easy. There were no complaints from the electrician.
The only other difference is our options of "recessed lighting" on the 2nd floor. We have a 2" space for fixtures. With the advances of LED lighting technology, we have decided to utilize LED surface mount lights that look like recessed lights by fit into standard Junction Boxes
These retail for about $25 each.
Whole House Ventilation
To ensure superb indoor air quality, the Zehnder HRV will ensure we have full exchange of all of the air in the house once every 3 hours with fresh filtered air.
A standard room 2 tube register
The 3" tubes are inserted to the register with a gasket
Each 3" tube is run separately back to the HRV
The tubes are then inserted back into the HRV with another gasket.
The red tubes indicate the "extract air" which will remove the stale air from the kitchen and bathrooms. The blue tubes will supply the fresh filtered air to bedrooms and living spaces. I will go into more detail on this system before commissioning.
We installed two 9000 BTU/hr Mitsubishi Mr. Slim heat pumps. I should note that only one is needed to meet the load requirements
This is the downstairs heat pump. It will basically be used for heating. It will probably only need to do some cooling when we have a large party.
This is the upstairs heat pump. It will basically be used for cooling only. Since cold air drops, getting the air conditioned air upstairs can be challenging for such a low flow ventilation system.
Stay tuned for another update soon as we will be holding an open house in the next week or so and finishing the insulation before drywall!