ROSE Construction Method Building Envelope+ w/HRV
The ROSE Construction Method Building Envelope+ has upper walls of double 2x4 stud construction with 7” of dense pack cellulose insulation combined with 3.5” of stone wool insulation (R40) for a total framing thickness of 10.5”. Lower foundation walls use ICF (insulated concrete forms) construction with 8” of concrete sandwiched between 5.5” of closed cell foam (R27). Primary roofs have 9 on 12 pitch wooden raised heel trusses with 24” min blown-in cellulose insulation (R60). Secondary roofs, walls, and closure zones utilize closed cell spray foam insulation. The lower level 4” concrete slab-on-grade floor rests on 6” of EPS rigid foam (R22).
The core of the home’s 1st floor level (bedroom, kitchen, living room & den) has Marvin Ultimate Tripane (triple pane) windows. The 12” long folding/sliding NanaWall door to the 3-season room is also triple pane. All other windows and exterior doors of the home are Marvin Ultrex double pane product line.
The Fantech whole house HRV (air-air fresh air heat exchanger) is a 92% efficient model SHR3005R.
E-Max Hybrid™ whole house geothermal-solar system
There are 13-300’ long x ¾” dia geothermal black plastic ground loops buried in a 12” thick wet sand bed making up the geothermal heat sink. These ground “slinkies” embedded in wet sand serve the same purpose as a drilled geothermal well system. The ground loop slinkies are filled with water and extract BTUs from the sand bed for heating purposes or deposit BTUs during cooling mode. In the E-Max Hybrid™ design there are also 13- 300’ long x ¾” dia red PEX solar ground loops buried 4’’ above the geothermal loops that connect to the solar thermal panels. The PEX loops are filled with glycol. The solar loops deliver additional BTUs (energy) to the heat sink when there is excess solar thermal energy available from the panels, and the glycol can be as hot as 200 deg F upon initial flow. Nine of the loops are located below the 4” concrete slab-on-grade (below the 6’’ of foam insulation) of the home, and four loops are located outside the foundation under 6” of foam and 10’+ of earth. The ground heat sink is the 3rd priority for the solar hot water controller after the first two have been satisfied (after DHW 1st and the Space Heating buffer tank 2nd).
The space heating buffer tank in turn is connected to the 2T water-water geothermal heat pump. As mentioned above, the buffer tank is also connected to the hot water solar panels via a common stainless steel heat exchanger so that excess hot water can be used to add heat to the buffer tank (2nd priority) before it heads to the ground heat sink (3rd priority). Under certain mid-day heating season conditions the hot water used for radiant floor heating may be provided solely by the buffer tank’s hot water from the solar panels when there is good solar radiation and moderate outdoor temperatures.
The 13 geothermal loops are connected to a common copper “manifold” that feeds into the two geothermal heat pumps. The geothermal heat pumps are both Bosch 2 Ton units (2T = 24,000btu). One is a water-water unit and is used solely for heating. It provides hot water to 10 zones of radiant floor heating lines on 2 levels, one Runtal radiant towel warmer zone in the MB, and one Buderus 198 gal solar storage tank zone (to maintain a min 100deg temp). The other unit is a water-air unit that provides both heating and cooling via an air ductwork distribution system hidden in the soffits of the first floor level. Nine of the room zones are controlled with the simplest “heating only” wall thermostats made, and can only control the radiant floor heat for that zone. The tenth and largest zone, located in the living room/dining room/kitchen area, is controlled using a sophisticated Ecobee thermostat/controller unit (the controller is located in the mechanical room). The Ecobee operates in all three usual smart thermostat modes (heating/cooling/auto) and can also be activated through the WEB on any browser enabled PC with user name and password or by Ecobee’s smart phone app. The two heat pumps are controlled independent of each other and any single zone thermostat (except the Ecobee zone) can be activated to provide radiant heat at the same time the upper level is in cooling mode, which could be a common operation for the solar storage tank “zone” during cloudy periods, but not so common anywhere else except for the occasional towel warmer zone use.
Solar thermal panels w/solar storage tank and on-demand (peaking) water heater
There are 9 Buderus Logasol SKS 4.0 solar flat plate collectors rated at 28,000btu/day located on the sloped house roof and connected to a Buderus PL750/2S Solar DWH/Space Heating Combi Tank holding 198 gallons in the mechanical room. The system is controlled with a Buderus TR0603 solar controller with two additional Buderus diverter valves.
The Seisco Model SH-14 four chamber tankless (peaking) domestic hot water heater has a max output of 47,780 btu at 14kw/240vac with a 95deg temp rise @1.0gpm. The Seisco unit connected downstream of the solar hot water tank and is automatically by-passed when the solar tank water temp is greater than 120 deg.
Solar PV or other renewable power for total electric annual (zero net metering) offset
There are 60 BP Solar PV panels (the solar array) located on the south side of the 45 deg pitched roof of the detached carriage garage. The panels are rated at 230 watts DC for a total installed capacity of 13,800 watts DC or approximately 12,000 watts AC. Three Solectria 4,000 watt AC inverters are connected to the PV array and then to the utility grid through a by-direction smart meter (net metering). A bank of 16 DC 60 amp-hours batteries are also connected to the PV system through two Outback 3,600 watt DC inverters and supply up to 7,200 watts of back-up emergency power should the utility grid go down. One 4,000 watt AC inverter remains active during a utility outage to supply real time AC power to the house and also to recharge the DC battery system. A 6,500 watt back-up gas fired generator is also located outside the garage to help recharge the batteries if a prolonged outage occurs and the DC batteries fall to 70% of their amp-hour capacity.
Measured Performance to date
The independent Energy Star rater for Unitil Electric gave the project a HERS index rating of 2.0, (i.e 0.0 is theoretical Zero Net) on a scale of 0 to 100, so our targeted “zero net” goal was accomplished. The 12 kw PV system was calculated by the rater to offset the last 33% of the HERS index.
The air leakage rate was measured at 0.60 ACH @ 50pascals (454 CFM on a volume of 45740 cubic feet of conditioned space), which meets the Passive House ( Passivhaus in German ) standard for air leakage and the most stringent used anywhere.
The 12.0KW AC solar array has been operating flawlessly since the first week of December, 2011. During the first 12 months of operation the system generated a total of 16,220 KWH