What is a Zero Energy Home
What is a Zero Energy Home and how do we design new homes to plan for a net-zero ready home in the future? Those are two big questions being talked about a lot lately. So I thought it was time to write a little on the subject of what a zero energy home was and how you could plan and build your new home to be ready for a zero energy future.
A zero energy home is a 100% self-reliant home, that means it was designed and built with the leanest energy use design and products available so that it is capable of producing or more accurately collecting what little additional energy it needs from sources like the earth (geothermal), the sun (solar energy collection), wind (wind powered turbine electricity), or from water (hydro-electric equipment).
This is basically what people are talking about when they discuss going off the grid. Sounds kind of science fiction doesn’t it? Not really, you see it is projected that within the next 20 years or so almost all of us will be able to live “Off the Grid”. So the question to consider is will you plan for this future or will you pay a higher price to convert in the future?
I’m going to talk about the different things that you should consider and implement today to prepare your new home or home upgrade for a zero energy home future. After that I will include a checklist for building a solar ready home that was prepared by the EPA based on their Renewable Energy Ready Homes (RERH) Specifications. This way you will be better aware of how easy it could be to prepare your new net-zero ready home.
Zero Energy Home and Building Orientation
The first topic on our list to preparing a zero energy ready home is talking about building orientation. Building orientation refers to the direction each side of your home faces. This becomes very important when planning for things like numbers and sizes of windows and which direction they will face and how overhangs and shading will affect solar heat gain both in positive and negative ways. It will also affect things like planning and placement of future roof mounted solar panels as far as direction and roof pitch.
Because many people are building in modern developments it is not always possible to orient the home in the most desirable direction. When this is the case it is especially important to study the building orientation and use creative planning to achieve the best possible outcome. Try and find a Zero Energy Home Builder or look for Zero Energy Home Plans that will suite your building site.
The bottom line here is to take a close look at your building orientation options and plan as well as you can for long term positive energy saving results.
In the home building industry you will hear the experts use the phrase “Build it tight, vent it right”. These after all are the two most important aspects of building towards a zero energy home today.
Without building an air tight well insulated building envelope you will find it virtually impossible to create a home ready to meet the zero energy requirements of tomorrow without spending unrealistic amounts on alternative energy sources. It’s good to know that our goal here is to create a home that needs a minimal amount of alternative energy to sustain itself.
So here is a list of the main things to plan into your new home to prepare it for the building envelope segment of planning for a net-zero home.
- You need a continuous air barrior from the basement slab through to the attic floor. This means that you need to caulk or air seal even the smallest of cracks at every joint in the wall system from the very bottom to the very top. In addition the entire envelope should be sealed with an approved housewrap product. (Remember that you can never go back and fix many of these energy loss sources you will just have to live with the added energy cost for the life of the home.)
- Advanced framing is next on our list, advanced framing is the practice of stacking stud and joist locations so that you get maximum support with minimum material. The idea here is that the wood in your framing will transfer heat faster than your insulation so the studding and plates in your walls are the worst part of your energy envelope. (read more on advanced framing techniques)
- Proper insulation around openings and outlets. This one should go without saying but it is a common problem to place over compressed insulation in these areas and this will restrict the insulation value in these critical locations.
- Proper draft stopping, this is the practice of enclosing all fiberglass and blown cellulose insulation in walls on all six sides. It is a common oversight in double wall areas or areas of ceiling change to miss this. In these areas it is important to draft seal all sides of the insulation with a solid air sealed wood or drywall sheeting to act as a draft stop.
- If you are doing recessed light fixtures make sure you are using units approved for an insulated area and make sure to properly install the air tight gaskets around the trim rings. Failure to use the correct fixtures or correctly install these airtight rings will result in a large amount of energy bleed.
- Attic hatch or attic stairways pose a different air leak concern. Make sure the attic hatch door or stairway door has a proper air seal gasket and that this gasket is fully engaged every time the hatch is closed to help prevent air bleed at this location.
You should plan to treat the above processes as a separate part of the scope of work on your new home. These seem like small details but they are very important and some of them are time consuming. This is why they are often overlooked in average home construction.
Zero Energy Home and HVAC Systems
Your HVAC system (Heat, Vent, Air Conditioning)is a very important part of the overall energy efficiency of your new home. One of the biggest mistakes in modern construction is oversizing an HVAC system. You should insist that your equipment and ducting system are properly designed using the Manual J(heating and cooling load calculations) specific to your homes exact location, size, design, and construction materials and practices used.
Getting your ventilation system designed and set up right is critical to creating a zero energy ready home. It is common to find one of three venting systems used in a new home. Either exhaust venting, supply venting, or balanced venting. For the purpose of time here we are going to recommend that you investigate balance venting since this practice covers both the required venting for your path to a zero energy home and it also takes care of the very often overlooked topic of indoor air quality.
Zero Energy Home and Energy Production
The last piece of the puzzle will be when you are ready to add in an energy production system. The key here is that it has been estimated that you will need to achieve a HERS index of around 55 before you can effectively expect good return or your energy production costs. Anything response higher than that on your HERS rating and you are wasting more energy in your homes envelope than you can replace with practical means.
In the beginning of this article I promised you information on the EPAs Renewable Energy Ready Home Specification Checklist. Her is a link that will bring the printable checklist up in PDF format directly from their web site. EPA Renewable energy Ready Home Checklist