In this article our goal is to provide you with a basic understanding of popular heating/cooling/ventilation solutions for high-performance homes, so you can engage in informed discussions with the consultant or designer/builder you’re considering for your custom home or remodel.
Consultants, designers and engineers, and builders of high-performance homes have considerable latitude in the approaches, mechanical solutions and materials used in achieving their desired energy targets, and often there is a cross-over between approaches. The BC Energy Step Code is targeting 2032 as the year all new buildings must be “net-zero energy ready”.
As demand for high-performance homes grows, we’re seeing a range of standards and certification labels emerge, including Built Green®, CHBA Qualified Net Zero Home, Energy Star, EQuilibriumTM, LEED, R-2000 and Passive House. The two most common performance approaches on BC’s West Coast are Net Zero and Passive House.
Net Zero approach
A Net Zero home produces as much energy as it uses on an annual basis, so it’s not a drain on natural resources. Detractors have argued that any home can be made net zero simply by bolting enough solar panels to the roof. While most net zero homes do have a roof-mounted solar photovoltaic (PV) system, they are generally designed from the ground up to be very efficient.
In a well-designed net zero home, every component should work together to ensure top performance. These typically include the air-tight building envelope, insulation, mechanical system and renewable energy system. Most conventional Canadian homes are using roughly half of their energy consumption on space heating; which is about four times that of an energy efficient net zero home.
In Canada, most net zero homes produce a surplus of energy in the summer and need more energy than they can produce during the winter months. They use the solar “credits” produced in the warmer months to offset the energy they need in winter. Another option is storing surplus electricity generated on-site in batteries, for use during peak hours and blackouts.
Net Zero homes incorporate a superior building envelope that separates the indoor environment from the outdoor environment. This can be achieved through airtightness and high-performance insulation of the exterior walls, floors, ceilings and foundation, as well as windows and doors. Designing a better envelope eliminates drafts, helps maintain an even temperature throughout the home and blocks out most of the exterior noise. Less energy is needed to offset heat loss in winter and heat gain during the summer.
The HVAC (Heating, ventilation, and air conditioning) mechanical systems are generally smaller in net zero homes. The heating and cooling is usually handled by an electric air source heat pump (ASHP); typically with a backup forced-air natural gas or electric furnace. If the envelope was designed to be airtight, a mechanical ventilation system should be added to continuously replace stale air with filtered fresh air. The home’s water is usually heated with a condensing water tank or instantaneous tankless water heater. Solar water heaters can be added to further reduce energy consumption.
Most net zero homes are equipped with an energy monitoring system to track the energy used, and where applicable, the renewable energy produced that is being fed back to the energy grid. Some control panels can also help locate phantom energy usage.
Passive House approach
The Passive House high-performance building standard is currently the only internationally recognized, proven, science-based energy standard used in construction. Certification ensures that Passive House designers and consultants are expertly qualified to design buildings that meet the standard. Passive House standards focus on energy efficiency, although they may at times incorporate a sustainable energy source into the design to qualify as net zero ready too. Passive house buildings consume up to 90 percent less heating and cooling energy than conventional buildings.
The international Passive House (Passivhaus) standard specifies:
- a space heat demand maximum of 15 kWh/m2a OR heating load max. 10 W/m2,
- a pressurization test result at 50 Pa max. 0.6 ACH (both over-pressure and under-pressure), and
- a Total Primary Energy Demand maximum of 120 kWh/m2a
Passive houses always use an airtight envelope. Focusing on the building envelope not only leads to big energy savings but also improves comfort, while reducing noise levels. Thermal bridging is minimized and walls are designed to make sure vapour can escape, but warm air does not. The walls are super-insulated and windows triple-glazed for heat retention, and much of the heat inside the home typically comes from the sun, appliance use and even body heat. Super insulation combined with passive solar design and thermal mass can maintain comfortable indoor temperatures considerably longer than conventional homes during power outages.
Most passive houses are orientated on a north-south axis, with most windows facing the south to maximize passive solar heat gain. Windows on the south side will usually be detailed with overhangs on the exterior to allow as much sun as possible to enter the home during the winter months when the sun is at a low angle. Then during the hotter months, when the sun is higher, the overhangs block the high summer sun. Making effective use of daylight can also provide a more pleasing indoor environment.
A heat recovery ventilation (HRV) system removes stale air and continually replaces it with fresh air while recovering up to 85% of the heat from the outgoing airstream. The incoming air is filtered to remove pollutants, dust and pollen from the air. The heat from the exhaust air is recovered by preheating the incoming fresh air. The ventilation system runs at low speed continuously throughout the year.
Heating, cooling and ventilation solutions
A heat pump is an energy-efficient alternative to conventional heating systems like a forced-air natural gas furnace, radiant floor heating or electric baseboards. Choosing a heat pump, instead of relying on fossil fuels like natural gas, propane or oil, reduces your household’s environmental footprint significantly.
A heat pump can provide year-round comfort, with heat during the cooler months and cooling during the hot ones. A heat pump is powered by electricity and moves heat from one location to another. During the winter months, it pulls warm air from outside and moves it indoors to heat your home. During the summer months, it moves warm air from the inside to the great outdoors.
Heat pumps typically use 50% less energy than air conditioning during the summer. Moving warm and cool air around, rather than generating heat with electrical baseboards or radiant flooring, is up to 300% more efficient. In Vancouver and the Sea to Sky Corridor, an air-source heat pump (ASHP) is usually your best option. ASHPs take heat from the outside air and move it indoors.
There are three common heat pump configurations. Mini-split heat pumps don’t require any ducting and are often known as ductless systems. They utilize an outdoor unit that gathers heat from the air and transfers it via refrigerant lines to one or more heads mounted inside, for a multi-zone heating or cooling solution. Central heat pump systems also have an outdoor unit, that connects to an indoor unit, and then moves hot or cool air throughout the house via ducting. Ducted mini-split heat pumps work the same as conventional mini-splits, but have an additional hidden head that distributes warm or cool air to two or more rooms. Ducted mini-split systems are popular for upper floors, where the hidden head is placed in the attic, and ducting delivers air to the rooms on the top floor.
HRVs and ERVs
A ventilation system will keep the air inside fresh, removing pollutants and allergens while managing the humidity level to some degree. Both HRV and ERV reclaim energy from air exhausted from your home. The incoming fresh air is either warmed or cooled, depending on the season or weather.
A heat recovery ventilation (HRV) system supplies fresh air to the living spaces where people most often congregate, like bedrooms, living and recreation rooms and kitchen/dining areas. It removes stale air from rooms with higher humidity levels, like the bathrooms and the laundry room. During the summer, the incoming air is cooled, and during the winter it is heated.
An HRV is made up of two air ducts, with one bringing air inside, and the other carrying the exhausted air outside. Both the incoming and outgoing air pass through a heat exchanger. The exchanger transfers heat between the two airstreams without allowing them to come into direct contact with each other. The speed of the fan in each duct is regulated, depending on the temperature and humidity levels.
During hot summer days, the HRV can pre-cool the fresh air that is entering your home through your air conditioning system. In winter, the HRV will recover heat energy through the heat exchanger, using it to preheat the fresh incoming air.
The efficiency of the HRV system can minimize the carbon footprint of your house, retaining nearly 85% of the heat from the exhausted air, while also minimizing carbon dioxide levels. Even though the fans run constantly, they consume very little energy; roughly 13 watts of electricity. Moisture is typically vented out of the home with fans in the bathrooms, kitchen and laundry rooms, to help prevent mould and mildew, while filters on the HRV remove pollen, dust and pollution from the incoming air.
An energy recovery ventilator (ERV) system also recovers heat; however, it also recuperates the energy trapped in moisture, which can greatly improve the overall recovery efficiency. In the colder months, some of the humidity in the air indoors is retained, for greater comfort and to minimize static electricity; and during the warm months, the ERV usually pulls in outdoor air.
The big difference is moisture recovery. An ERV monitors humidity levels and can either retain or eliminate humidity by transferring moisture from one airstream to the other. This humidity control function can improve the comfort level in your home while keeping the heat exchanger warmer. This improves its efficiency and reduces energy costs.
In a humid area, or in homes with more people, an ERV may be the better choice. The more people living in the house, the more humidity will arise from breathing, cooking, showers, and laundry.
ERV systems do require more maintenance than HRVs, they usually cost a bit more upfront, and the installation is more complex. Like HRVs, they filter pollen, dust and pollution from the incoming air.
Electric and hot water post-heaters
Electric post-heaters are often used alongside an HRV or ERV system. Post-heaters are commonly duct-mounted and heat the air supply as it leaves the ventilation system. Electric post-heaters react to supply air temperature changes in the ventilation exchanger.
Hot water post-heaters are also positioned within the supply duct of an HRV or ERV system. The primary advantage of a hot water post-heater is steady integration with the home’s hot water heating systems.
Solar heating systems – aka solar domestic hot water systems, or SDHW – use fitted panels called collectors. The heat from the sun transfers to the water, which is stored in an insulated hot water cylinder or storage tank. Roof-fitted solar solutions benefit from very low running costs and versatility. The hot water can be used with HRV post-heaters, in underfloor heating and/or radiant heating panels.
Energy demands in high-performance homes can be so low that an SDHW system has the potential to cover 60% of the heating requirements. According to the Government of Canada, an ENERGY STAR® certified solar water heater uses 60% less energy, on average than a standard model. Because solar heating is dependent on the sun, solar heating is typically used in conjunction with an electric heating solution.
Natural gas or propane boilers are a conventional way to provide heat in every room as well as hot water. They are still an option for passive houses. Net zero homes rely on electrical or solar heating to utilize the renewable energy their home generates, so gas is not an option.
Gas boilers are very affordable, and offer a wide range of heat distribution options, like baseboard radiators and underfloor heating. Gas prices fluctuate, so higher energy costs are likely to more than offset a lower initial investment. Another consideration is that evolving BC Energy Step Code requirements could potentially demand swapping out a gas boiler for an electrical one before 2032.
Radiant heating can be infrared (electrical) or hydronic (water-based). There are air-based radiant systems, but they rely on a traditional forced-air furnace. Radiant heating is clean, silent and offers the reliability you’d expect from having no moving parts.
Electrical radiant heating systems generally are made up of specially designed plasterboard panels that are inserted into walls and ceilings of the house, or through cables installed between the floor and subfloor.
A bathroom or kitchen heated with radiant heat panels will warm a tile or slate floor similar to that of having in-floor heating but without the high installation costs. Infrared heating panels are fully compatible with renewable energy sources such as solar or wind power.
Hydronic or water-based radiant systems rely on a central boiler to heat the water, which is then circulated through tubing installed between the floor and subfloor or in the walls. Passive houses that use natural gas boilers may include hydronic radiant systems, but high-performance homes usually have an electric boiler or use a system that combines an electric boiler with solar heating. The one concern many homeowners have is the potential for a water-based system to develop a leak.
There isn’t a standard one-size-fits-all approach to designing a high-performance dream home. Heating, cooling and ventilation solutions are combined to arrive at the efficiency target. As the future homeowner, you want to be involved in the series of decisions that ultimately will give birth to the home your family will live in.