We have some preliminary renderings of the project by Rick Mullen. Things are progressing nicely as the three energy use models are getting assumptions aligned. We are starting to learn some things about how the house will act. We have decided on the basic envelope design. We are using advanced framing with 2 x 6 studs on 24" centers. Blown in cellulose will fill the wall cavities and 2" of EPS foam will go over the sheathing to add R-value and a thermal break. We plan to be fastidious about detailing with gaskets and caulk, to reduce air infiltration as much as possible. These are decisions that fit into the budget. When it comes to the heating system and windows we have to begin a careful cost benefit analysis. Ideally we would use R-5 windows and possibly a ground source heat pump. These options may be out of reach in our budget so creative solutions will have to be explored to achieve the Net Zero goal.
We are putting much of the project out to bid this week and will have better cost numbers soon. Once we have firm pricing for the shell and basic services in the house, we can see what is left for upgrades in energy conservation,reduced water use and long term durability.
I am posting our original thoughts and ideas below, prior to energy modeling and pricing. It will be interesting to see what ideas and products carry through into construction.
Energy Measures for KCLT Net Zero Home
8.24.09
Goal: To achieve an annual balance of energy consumption and on-site energy production resulting in net-zero energy use and cost to the homeowner over the course of a year. This will be achieved through the combination of homeowner conservation, passive solar design measures, energy efficient construction methods and materials, and on-site production of renewable energy.
Specific measures include the following:
Homeowner Conservation: “Conservation is the cheapest form of energy”
1) Educate homeowner about energy and water conservation methods – provide manual of energy saving tips.
2) Provide a meter in the home which homeowner can use to monitor actual real time energy usage TED – The energy Detective – can tell when you are producing or using energy and encourages homeowner to strive for net-zero.
3) Consult with local utilities to measure and evaluate and compare energy usage to local averages – Discover and set reasonable goals, seek out financial incentives for homeowner. Monitor to determine if performance matches goals.
4) Provide cellular shades for all windows which homeowner can use to control heat loss and gain.
5) Provide zoned heating system with programmable thermostats
6) Choose appliances that avoid phantom loads – unnecessary clocks, etc.
Passive Solar Design: LCLT goal 40-50% reduction of heating loads through passive measures
1) Design smaller than average homes – use less resources and energy from the start.
2) Orient house to take advantage of passive solar heat gain and minimize heat loss – general east-west axis, most glazing to the south, maximum 20 foot deep allows solar energy and natural light to penetrate deep into house
3) Glaze S, E, and W to capture solar heat, Glaze North to hold in solar heat.
4) Use exposed concrete slab to act as thermal mass to store and temper solar heat gain.
5) Design overhangs and shading devices to maximize solar heat gain in winter and temper gain in summer.
6) Use energy modeling and 3D modeling during design to determine optimal amount, size, and location of glazing and shading devices. Also optimal amount of thermal mass and benefit derived from these measures.
7) Align windows and doors for abundant natural light and passive cooling
Energy Efficiency: highly insulated, tightly sealed shell with max. efficient appliances and lighting.
1) Utilize 24” o.c. advanced framing to reduce thermal bridging through studs
2) Use high performance and above code required insulation values, min. R-10 rigid foam under slab, min. R-21 blown in cellulose in walls with rigid foam outside sheathing as well to prevent thermal bridging through studs., min ? R-50 blown in cellulose in attic.
3) Use advanced air sealing techniques to reduce infiltration. Conduct blower door tests and infrared analysis after enclosure and prior to hanging drywall to find leaks – caulk and seal.
4) Windows and doors – evaluate U-value, SHGC, and VT for each façade. Use energy star rated windows and Low –E glazing.
5) Use energy star rated appliances with low energy settings, consider cold water feed to front loaded washer only. Dryers are energy hogs – get one with moisture sensing feature.
6) Use energy star rated lighting – CFL or LED. Outside lighting use light or motion sensors.
7) Use low cost/low noise electric radiant heat with zone control and programmable thermostats. No duct work or mechanical space required. No cooling required in our climate. See www.heatinggreen.com and ConvectAir heaters. Possible electric radiant floor mats in bath under tile?
8) Look at Thermomax solar hot water systems. Can provide 65-75% of HW requirement. Get it SRCC OG-100 certified. Evacuated tube system closed loop with pressurized glycol plus electric resistance storage tank with heat exchanger. Consider HW recirculator at special locations?
Renewable Energy: after conservation measures, passive design, and energy efficiency measures have been exhausted meet remaining energy requirements with renewable energy.
1) Consider installing a grid tied solar PV array and inverter. Sells surplus energy to grid, uses grid as storage device. As a min. wire house to be PV ready in future.
2) Use energy modeling in design to predict loads, size PV system, compare relative energy costs, payback period.
3) Have homeowner purchase remaining energy from renewable sources program of PSE.
Next week we will know more.
