NET-ZERO THE SUPERHERO – What It Is, And How To Build It

| by Melissa Baldridge
NET-ZERO THE SUPERHERO – What It Is, And How To Build It

Net-zero is the new superhero, and building to simply pass building code is for mere mortals.

“Net-zero” homes and buildings can be defined a lot of ways – in terms of energy, water, carbon emissions and waste streams. But for the purposes of this post, I define it with energy use – the energy required to heat, power and cool a home is completely offset by energy savings and renewable energy. Thus, netting out at zero.

(Also, I assume, dear reader, that you understand the HERS index and energy modeling. If not, please visit my previous post on this, or go to HERSIndex.com.)

It is absolutely possible to build net-zero (NZ) with conventional sticks and bricks, and I routinely see HERS-rated homes built (BUILT) in the mid- to low-40s. For this article, I created a HERS energy model of 45, and dropped it to zero (available at end of article).

One rule of thumb – if builders used a strategy to passively heat and cool 150 years ago, it’s something to consider today.  Like my first point below ...

  1. OVERHANGS – Generous eaves and overhangs help shield a home or building from hot summer sun, and as winter the sun is lower in the North American sky, buildso that it passively heats a home’s interior. In my climate zone (Denver, CZ5B), the sweet spot for overhangs seems to be 2 feet (or more) on every side, except the south, which needs 3 feet. If you must skip a side, leaving overhangs off the north side doesn’t impact the energy model.
  2. LIGHTING – With the drop of LED prices (now below $5 for a bulb), there’s no excuse to forego LED lights anymore. They’re gorgeous, rarely require changing, and can easily be looped into home automation systems. The CFL bulb was always meant to be a bridge solution, but instead became the hated the poster child for government interference in efficiency standards. While I do see some clients still use them, most builders and lots of homeowners have stepped up to LED.
  3. BUILDING ENVELOPE LEAKAGE – If there is one aspect of green build I can point to that makes the biggest difference: it’s “envelope leakage” – how leaky a building shell is. Other energy-efficiency fixes usually ride the coattails of this, and if you don’t reduce air leakage, you’re not doing the work that matters.
  4. INSULATING THE “RIM & BAND” – The “rim joists” are the floor supports that sit atop foundation walls, and the “band joists” are the same for upper stories. If youwant to drop a home’s energy use, these critical areas need to be spray-foamed. Mechanical piping and utility service enters most homes at the rim, and it’s usually the leakiest area.
  5. WHOLE-HOUSE VENTILATION – Seems counterintuitive to seal a house against air leaks. And then add air. High-efficiency ventilation systems like heat- and energy-recovery ventilators (HRVs and ERVs) recycle warmth in a home while exhausting stale, unhealthy air. They also drop energy ratings a lot.
    REAL ESTATE IMPACT – For average buyers, there may be one or two efficiency features they notice when they buy a home, and shiny, happy E-STAR appliances are one of them. Install them whenever possible, and market them. The Environmental Protection Agency has spent a mint promoting the brand – leverage that in your sales.
  6. ENERGY STAR APPLIANCES – The Environmental Protection Agency, which oversees the ENERGY STAR brand, continues to raise the bar on appliance efficiencies, and raise the bar. Installing E-STAR appliances and systems is a brilliant way to stay abreast of efficiency advances.
  7. FIREPLACE – Here and in other cold places, we use fireplaces to heat homes, and there are higher-efficiency ones than others. Check the efficiency ratings or “steady-state” efficiencies for fireplaces in new builds or renovations. They will carry part of the heating load so you might as well pick ones that do that well. (Look for those that sell in Canada where efficiency requirements are more stringent.)
  8. HIGH-EFFICIENCY HOT WATER HEATERS – There are some smokin’-efficient hot water heaters out there, including “heat pump” units that have 300 percent efficiency. But electric models like that also use expensive energy. Check out high-efficiency gas tanks, or even tank-less. With the latter, you’re not heating a tank of water 24/7.
  9. WALLS – The less lumber you use and the more space you create in wall cavities, the more insulation you can install. Talk to your builder about building 24 inches “on center” – center of wall stud to wall stud. What I routinely see is quality builders building this way with thicker drywall (5/8 inch) to better mask uneven framing. 

    REAL ESTATE IMPACT – If owned, solar arrays can add tens of thousands of dollars to a home value at sale and appraisal.New Fannie Mae guidelinesmake this clear for appraisers. If you lease a system or have a PPA, it’s more of a crap shoot.


    10. And lastly, SOLAR – If you build the most efficient conventionally framed home today, the HERS rating will be in the ‘40s. Solar makes the rest of a home’s energy use vanish. And that’s the goal.

To write this post, I created a 2,600-square-foot home with high-performing features like these. If you’d like an oversize graphic of that house and a copy of the HERS energy model certificate, email me. I’ll send it to you.

And if I can help you with your home’s specific features, reach out.


Topics: Building Green, Certification / LEED, Energy Audits, Energy Star, Going Green, Healthy Homes, Home Design & Plans


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