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According to the US Environmental Protection Agency (EPA), space heating constitutes 42% of the energy consumed in an average US home.

With fuel prices on the rise and more people becoming environmentally conscious, there’s been a significant increase in interest regarding net-zero homes. As a result, most homeowners are looking to figure out how they can heat their homes while still achieving their net-zero goals. 

Net-zero houses are planned and built to maximize solar heat gain during winter days and then store the collected heat to distribute it later throughout the house after sunset.

Although net-zero houses have to conform to strict energy efficiency standards and are costlier to build, they pay you back in reduced utility bills.

How Do You Heat a Net-Zero House? 

Here are ten steps you can take to heat a net-zero house.

  1. Use Energy Star-rated heating appliances.
  2. Install south-facing windows to collect solar heat.
  3. Store the accumulated heat in a thermal mass.
  4. Distribute the heat throughout the house.
  5. Insulate to prevent heat loss.
  6. Ensure cold air does not enter the house.
  7. Install a ground-source heat pump.
  8. Install solar panels.
  9. Install a heat recovery ventilator. 
  10. Plan the interiors to maximize solar gain.

1. Use Energy Star-Rated Heating Appliances

Installing an Energy Star-qualified heating appliance is the easiest and quickest way to start your net-zero journey. 

The Energy Star logo guarantees that the appliance fulfills the strict criteria for energy efficiency. Additionally, consider buying ‘smart‘ devices controlled by smart electric meters or home energy management systems to regulate energy consumption.

Keep your high-efficiency heating appliances operating optimally by taking the following precautions.

  • Clean or replace the filters on furnaces as recommended.
  • Clean baseboard heaters, radiators, and warm-air registers as required. 
  • Let trapped air in hot-water radiators escape once or twice during the heating season. 
  • Finally, keep the area around vents and radiators free of objects like furniture that can obstruct the flow of warm air.

2. Install South-Facing Windows to Collect Solar Heat

A south-facing window or glazing is an integral component of passive solar heating in net-zero houses.

A south-facing window collects solar heat in the northern hemisphere, where the southern side receives sunlight throughout the day. This is called direct solar gain.

A south-facing window in a net-zero house..

Here are a few pointers to keep in mind while installing south-facing windows in a net-zero house:

  • Check with your local authorities if there are any limitations on the amount of direct-gain glass area, a regulation enacted to prevent overheating.
  • The south-facing glass should be aligned within 30 degrees of true south.
  • Trees or other buildings should not shade the glass from 9 a.m. to 3 p.m.
  • While tilted glazing is more effective than vertical glazing at collecting heat, the former is difficult to shade during summer.
  • Vertical glazing is almost as effective as a heat collector as tilted glazing in winter and is also easier to shade during summer.

3. Store Collected Heat in a Thermal Mass

Thermal mass stores the collected solar heat during the day and releases it to warm the interiors when the sun goes down. It is an integral component of almost all net-zero houses that employ passive heating approaches.

Thermal mass can be brick, stone, concrete slab, concrete masonry, tile, adobe, or water. 

Although water is more efficient at storing heat than other materials, it is challenging to install this feature in a house and requires specialized construction. On the other hand, masonry is easy to install and doubles as a sturdy structural or finish material. 

Here’s what you need to keep in mind while installing a thermal mass:

  • If you live in the northern hemisphere, the thermal mass should be on the south-facing wall of the house. 
  • Increase the efficiency of the thermal mass at retaining heat by insulating its outer surface, which is exposed to the outside air. 
  • The denser the thermal mass material, the more heat it can store.
  • The darker the color of the thermal mass, the more heat it can absorb. 
  • You can build a masonry fireplace or an interior wall to add more thermal mass.

You can also add thermal mass to your flooring. It should be about four inches thick (10.16 cm). 

Ensure that the bottom edge of the south-facing window is no more than six inches (15.24 cm) above the floor, guaranteeing the floor receives optimal solar radiation. 

4. Distribute the Heat Throughout the House

You might want to transfer the heat collected during the day to the living areas you use during the evening and night. 

Here’s how you can distribute the stored heat throughout the house:

  • Use small fans or blowers to move hot air from one room to another. 
  • If you have forced air, ensure that the ceiling fan rotates clockwise at a low speed to push warm air down towards the floor.
  • Direct a box fan towards the fireplace or a wood-burning stove to draw warm air into the room.
  • Install a vent over your heating appliance to move warm air throughout the room. 
  • Install a zoned heating system and multiple thermostats to regulate and maintain even temperatures throughout the house.
  • Ensure that no object is blocking the vents that blow warm air into a room. 
  • Go in for an open-plan layout to encourage unrestricted circulation of the collected solar heat throughout the house.  

5. Insulate To Prevent Heat Loss

Preventing heat loss is a critical consideration in a net-zero house, as the primary source of warmth, the sun, is available only during the day. The house must be designed to retain the captured heat for about 16 hours. 

Here’s how you can achieve superior thermal insulation in a net-zero house:

  • Install double or triple-glazed windows. 
  • Use carpets, heavy curtains, and draught excluders. 
  • Use spray foam insulation to prevent heat loss through walls. 
  • Insulate the attic and crawl spaces. 
  • Install loft insulation to avoid heat loss through the roof.
  • Insulate the ground or any floor above unheated spaces like the garage using area rugs or carpets.
  • Finally, insulate tanks, pipes, and radiators. 
A worker lifts a batt of rockwool insulation off a stack as he readies it to be applied to an attic ceiling

6. Ensure Cold Air Does Not Enter the House

To conserve warmth and save on utility bills in net-zero houses, you must make them airtight. An airtight home does not let cold drafts from outside enter the building or the warm, conditioned air from inside escape out. 

Here’s how you can make your house airtight:

  • Check for cracks, gaps, and air leaks around doors and windows.
  • Caulk and weatherstrip around doors and windows to seal cracks. 
  • Install heavy drapes and curtains made of fabrics like velvet or that have a thermal lining.
  • Caulk and seal around pipes, ducts, and electrical wires that come through walls, ceilings, floors, and soffits over cabinets.
  • Install foam gaskets behind power outlets and switch plates on walls. 
  • Insulate the attic. 
  • Use area rugs to insulate the floor and prevent cold air from entering your home through floor cracks.
  • Check the dryer vent covers for cracks and re-caulk if necessary. 
  • Install an inflatable chimney balloon when you’re not using the fireplace. 

We also wrote up a pretty detailed Ultimate Guide on Air Sealing Your Home if you’d like to check that out here.

7. Install a Ground-Source Heat Pump

Regardless of how cold it is above ground, the temperature just a few hundred meters below it is at a constant average of 55°F (12.78°C) throughout the year. 

Ground-source or geothermal heat pumps extract the heat stored underground and pump it back to the house to heat its living spaces. The unit consists of a network of pipes through which a conductive fluid flows. 

During winter, the fluid extracts warmth from underground, carries it into the house, and warms the cool indoor air. After losing heat, the fluid flows back underground to extract more heat.

Geothermal heat pumps are suitable if:

  • Your local jurisdiction permits their installation. 
  • You plan to live on your property for a few decades, which allows you to recoup the cost of the system.
  • There is enough space outside your home to install the system’s components.

In conjunction with adequate insulation, a geothermal heat pump can completely do away with using a gas-fired boiler.

8. Install Solar Panels

According to the US Energy Information Administration, a residential solar-powered system can produce 350-850 kilowatt-hours of energy per month. Every kilowatt-hour of solar power generated reduces the amount of greenhouse gas emissions significantly. 

Not all net-zero houses have solar panels. However, solar panels help you achieve your net-zero goals by producing energy for heating. 

A worker installing solar panels on the roof of a net-zero home.

Consider installing solar panels if:

  • Your state or city permits such installations.
  • The roof of your house faces south, the direction that receives the maximum sunlight in the northern hemisphere.
  • Trees or other buildings do not obstruct your roof from 9 a.m. to 3 p.m. 

You can make your net-zero house even more energy-efficient and get closer to your net-zero goals if you install batteries to store excess solar energy that you can use when the sun is not shining.

9. Install a Heat Recovery Ventilator (HRV)

High levels of thermal efficiency in the form of tight doors and windows, insulating foam, and caulk keep a house warm when temperatures are frigid outside and prevent cold drafts from blowing in. However, an airtight home is also devoid of fresh air.

Without adequate ventilation, the air inside a net-zero house can become humid or contaminated with pollutants and toxic gases released by household appliances like water heaters and gas ranges.

In addition, excessive moisture tends to breed mold, mildew, fungi, and bacteria. 

Therefore, after you have implemented all measures to heat your net-zero house, you must take steps to create adequate ventilation. 

Installing a mechanical HRV in a net-zero house promotes healthy indoor air without compromising warmth. 

Here’s how a heat recovery ventilator works:

  • There are two fans in the unit—one fan lets out the stale household air, while the other brings in fresh air from the outside. 
  • The HRV also comprises a series of alternating pipes through which outgoing and incoming airstreams move but never mix.
  • The heat from the outgoing air is transferred to the incoming air as the two airstreams flow through the pipes. 
  • The heated air blows into the living spaces through air valves.

Some HRVs can recover up to 85% of the heat from the outgoing airstream. This feature makes them more energy-efficient and budget-friendly than opening a few windows to let in the fresh air and then cranking up the heater.

A closeup of the exchange mechanism of an HRV in a net-zero house.
The exchange component of an HRV

Keep the following in mind when installing a heat recovery ventilator:

  • The fresh air inlet should be located where there is plenty of fresh air movement and away from driveways, range hood exhausts, and laundry vents.
  • The conditioned air outlet of the ventilator should be connected to the return duct of your home’s forced-air unit.
  • The stale air from your home should be collected from a wall near the kitchen but ten feet away from the oven to prevent grease from entering the ventilator.
  • Install point source exhaust fans in all bathrooms.

10. Plan the Interiors To Maximize Solar Gain

You can plan your interior space of a net-zero house to maximize solar gain. 

The goal is to ensure that the spaces you use during the day receive maximum sunlight. Then, you can transfer the collected heat from these spaces to your sleeping quarters at night.

Here are some ideas on how you can plan the interiors to maximize solar heat gain:

  • Plan to have living areas and the kitchen along the southern wall. 
  • Designate the bedrooms to the northern side of the house, as you can stay warm and comfortable in bed without needing a lot of heat.
  • Build your kid’s rooms along the southern wall of the house if you plan to have them stay in these spaces for a long time. 
  • Since hot air rises, design your home so that the bedrooms are on the upper floor. 
  • Locate utility areas like storage spaces, bathrooms, laundries, and garages that require minimal heating on the west or southwest side of the house.

Overview

These are the primary goals of heating a net-zero house:

  • Capturing sunlight during the day while ensuring there is no overheating.
  • Storing the collected solar heat. 
  • Distributing the stored heat around the house after sunset.
  • Preventing warmth from escaping the building. 
  • Preventing cold air from leaking into the building.
  • Maintaining healthy indoor air quality and humidity levels.
  • Using renewable sources of energy for heating.

Take these steps to ensure a fully-functioning, energy-efficient net-zero home you can be proud of. Best of luck!

Sources

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