Small in size, but mighty when it comes to performance! This 850 square foot ADU / guest house was designed with so many features that make this home comfortable, healthy, efficient, and resilient.
Read more about all the features in this home and how they work below.
Health & Comfort
1. Kitchen - Induction stove - no combustion of gas inside this all-electric home. no open flames, safe to touch, easy to clean, and incredibly fast cooking.
2. Laundry room - Heat Pump Ventless Dryer - Better drying for fabrics. A Heat Pump pulls the water out of clothes like a dehumidifier rather than baking clothes in an oven like gas or standard electric dryers.
3. Air sealing throughout house – Reduced the air leaks in the house by 3x!
· First, we taped, caulked, and foamed the gaps, cracks, pipe penetrations and voids through the exterior wall prior to insulating. Then used open cell spray foam to fill the walls to Quality Insulation Installation (QII) standards. This is usually satisfactory, but we wanted to reduce leakage to make the house air as healthy as possible and be more energy efficient.
· Second, we worked with an Aero Barrier installer who specializes in air sealing even the tinies of leaks. They seal a giant blower door fan on the front door, pressurizing the house like a ballon and then a machine sprays nontoxic vaporized caulking inside. The pressurized air flows to the pin hole leaks and fills them up. We started with 5 ACH and went to 1.7 ACH. An Air Change per Hour (ACH) means the number of times per hour the volume of air in the whole house is exchanged with outside air. Outside air can either come from places we know or places we don’t know like gaps around windows and doors, around outlet covers, around can lights through the attic or up through the crawl space. Not knowing where the air is coming from is scary and not healthy, so it’s best to seal the house to manage how and where the air comes in which we did with the fresh air ventilation system.
4. Ventilation throughout house – To manage fresh air coming in and out of the house, a Panasonic ERV (Energy Recovery Ventilator) was installed. An ERV brings in filtered fresh air as well as extracts old air in a controlled manner. The ERV is essentially a giant bath exhaust fan that brings in the same amount of air that it takes out. While bringing in the fresh air, ERV helps match the outside air to the interior temperatures, so the HVAC system has less strain.
5. Natural or Low VOC finished materials.
Interior White natural plaster
Polished concrete floor – easy to clean, and less carbon footprint than any additional floor covering such as carpet.
Nakamoto Shou Sugi Ban siding – Heat treated Cypress, meets Programme for Endorsement of Forest Certification COC
Kebony decking – modified at cellular level, FSC certified Pine, (alternative to Ipe). The deck is on the roof above the carport to utilize the most space.
6. Interior wall sound attenuation – Since the 850 square foot structure is a small space, sound control was important to allow for each space to feel separate. Rockwool Safe and Sound insulation was installed in all interior walls. In conjunction with the dense plaster walls, each room feels private.
7. Infrared Patio heaters – 2 heaters were installed above the outdoor seating area. The infrared heaters directly warm the body not the ambient air. They are much more efficient and safer than gas.
Performance & Efficiency
1. Heat pump Water heater – The SANCO heat pump is nearly 300% efficient, a gas furnace is max 96%. Tank lives inside and compressor is outside. The tank is plastic so will never rust like a typical tanked water heater. Also, the refrigerant has a lower Global warming potential. It is CO2 (GWP of 1) rather than a chemical which could have a GWP of over 2000.
2. Samsung Mini split heat pump for HVAC – A ducted mini split air handler was tucked up in the small attic to provide heating and cooling to two bedrooms, two baths and kitchen/living room.
3. Weather shield Energy Star Aluminum clad Windows – Energy Star rates more than just appliances. These windows are low maintenance, resilient, and energy efficient.
4. Raypak Heat pump water heater for Spa – To heat the spa we used a Heat Pump in conjunction with the traditional resistance heater. The heat pump can maintain the water temp and the resistance heater is called when a boost is needed immediately.
Resiliency
1. SPAN panel – the smart electrical panel allows you to monitor and manage electrical needs from your phone. You can see usage, solar production, and battery performance. If there is an outage, you can adjust which are the most critical loads to back up on the fly from your phone rather than being limited to 2-5 circuits in a dedicated sub panel. This reduced the need for an extra subpanel and wiring as well as added ease!
2. Solar & Battery storage
· Flat roof filled with solar 9.6kw Solar and 7kw LG Battery
· We performed a load calculation based on the owner’s habits to determine the solar required.
· Last year, the project produced 89% of its own power, a major accomplishment towards NET ZERO. The rainy days really reduced solar production.
