How Much Does It Cost To Build A Net Zero House?

Envelope Components to Consider for Increasing Efficiency

 

• Insulated corners

• Insulated headers over windows and doors

• More space for insulation at intersections of interior and exterior walls

• Multiple layers of insulation; e.g., combining blown-in wall insulation with rigid exterior foam

• Continuous XPS barrier/thermal break

• Air gap between insulation and siding (this depends on your climate)

• Super-insulated attic

• The generous overhang above windows and doors help keep the weather out

• OSB roof sheathing with taped seams

•  Insulation in crawl space/basement

 

What’s On the Inside

When a tight, well-insulated envelope is put together in your house, it's time to consider the systems that keep the inside cozy, as well as the different appliances you need to get things done.

 

Ventilation: A Breath of Fresh Air

Did you know that much of an older house's fresh air comes from leaks? You have to give more thought to how fresh air will get in for good indoor air quality ( IAQ) without those old drafty doors and leaky windows. One way to get fresh air into the home without losing heat that has already been generated is through Mechanical Ventilation Heat Recovery Systems (MVHR Systems).

 

HVAC: Heating, Ventilation and Air Conditioning

 

Heat Pumps

Heat pumps are an incredibly powerful means of cooling your home and heating it. This is particularly true in warmer climates, however, combined with superior insulation, improving heat pump technology allows newer heat pumps to keep northern homes warm, too.

 

Simply put, by transferring heat from one region to another, heat pumps function: inside to outside for cooling, outside to inside for heating. Since it takes less energy to transfer heat than to produce it, it makes for an effective device. (Imagine running a regular air conditioner on a blazing afternoon in August. Fuel is being burned to produce heat energy to generate electricity somewhere far from your home ... to cool the house.)

 

Heat pumps from the air supply draw heat from the outdoor air to heat (because there is heat in the air, even though it feels cold outside) and release extra heat to cool the house back into the outdoor air. In most homes, they are the most prevalent kind and easier to build.

 

Land source heat pumps use heat from the earth to heat the building, and when cooling is needed, use the ground as a heat sink to release extra heat. While they are more effective than air-source heat pumps, they are more costly to install and need an appropriate location to bury the underground pipes needed.

 

In the U.S., the familiar heat pump is a large outdoor device that operates much like a conventional central air conditioner with an indoor duct system, except that it can also heat the home.

 

Ductless mini-split heat pump

When North Carolina's Habitat for Humanity of Catawba set out to create an inexpensive net-zero home, they chose a heating and air conditioning mini-split heat pump.

 

Like other heat pumps, a mini-split heat pump works, but does away with conventional ductwork and instead uses narrow refrigerant lines, removing a common cause of energy loss. One outdoor unit in various rooms inside the house is linked to indoor units, enabling individualized climate control for different areas. (It's helpful to know that for this device to function effectively, you don't need an indoor unit in every room.)

 

Sizing Your System

 

Experts agree that bigger isn't better, whatever kind of heating and air conditioning system you add. Make sure that your device is the right size for your house's floor plan-you'll both be more relaxed and save electricity.

 

Where Does the Energy Go?

 

It just wouldn't make sense to put in appliances that would guzzle electricity or gas with your energy-efficient house all set together.

 

The U.S. Energy Department offers an Energy Star award to appliances that meet a high-efficiency level. For any home appliance that you can think of (plus a few).

 

Water heaters get a special mention here because, as the main energy user, heating water comes right after heating and cooling living spaces. There are some great choices that are energy-efficient, including systems that work with your home heating system, solar units, and more.

 

Don't forget to mention the possibility of adding a clothesline to your backyard while preparing laundry. In summer, it will save energy and keep additional heat out of your house, plus you'll get a little exercise (with a free vitamin D dose).

 

There is also a handy device that you can mount on your dryer that helps you to retain the heat of the dryer inside your house during the winter, instead of directly blowing it outside.