musingsheader image
Helpful? 0

A Leaky Old House Becomes a Net-Zero Showcase

Renovators wrap a 1970s ranch house with a new SIP shell

Posted on May 14 2010 by Martin Holladay, GBA Advisor

Jane Bindley had a dream: to turn her 1978 ranch in central New Hampshire into a net-zero-energy house. How hard could that be?

As it turned out, pretty hard. But with help from a dedicated team of experts and a generous budget, Bindley achieved her dream.

Can a north-facing house be net-zero?
Bindley chose her team wisely. She hired a New Hampshire company, Garland Mill Timberframes, to renovate her home. Ben Southworth from Garland Mill is an experienced design/build contractor. When it came time to choose an energy consultant, Southworth advised Bindley to select Marc Rosenbaum, one of the most experienced designers of net-zero-energy homes in the country.

Southworth doubted that Bindley’s nondescript ranch was worth saving. “I told her, ‘It will cost more money to take it apart than to bulldoze it,’” said Southworth. “But she answered, ‘It’s structurally sound, and I can’t imagine putting the house in a landfill.’ ”

The house sits on the shore of Squam Lake, with a spectacular view of the lake to the north. Most of the home’s windows face the view. “We were killed from a solar perspective,” said Southworth. “The house is up against a big hill on the south side, and the hill has tall trees. We put as many PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow. panels as we could on the south roof. Since we were aiming for net-zero energyProducing as much energy on an annual basis as one consumes on site, usually with renewable energy sources such as photovoltaics or small-scale wind turbines., the PV array defined what our heat load had to be.” The house ended up with a 7.5-kW PV system.

Rosenbaum rose to the challenge. “The house has an incredible building envelopeExterior components of a house that provide protection from colder (and warmer) outdoor temperatures and precipitation; includes the house foundation, framed exterior walls, roof or ceiling, and insulation, and air sealing materials., which was an attempt to compensate for the drawbacks of the site and the north-facing windows,” said Rosenbaum. “The south roof gets a lot of winter shading. There was a low-slope roof with a 5/12 pitch, and we couldn’t raise the roof or the solar array because of zoning restrictions. So we needed a kick-ass envelope. The envelope specs came from doing the math.”

Creating a very tight, well insulated envelope
The home’s vinylCommon term for polyvinyl chloride (PVC). In chemistry, vinyl refers to a carbon-and-hydrogen group (H2C=CH–) that attaches to another functional group, such as chlorine (vinyl chloride) or acetate (vinyl acetate). siding and roof shingles were stripped and the interior of the house was gutted. Most of the materials removed from the house were recycled or reused.

Adopting the “chainsaw retrofit” approach, Southworth and Rosenbaum decided to cut off the home’s roof overhangs. Once the seams between the existing sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. panels were sealed with peel-and-stick tape, the roof and all of the exterior walls were covered with new 6 1/2-inch-thick structural insulated panels (SIPs). The urethane-insulated SIPs are rated at R-35.

Wrapping the home with SIPs was unusual; many builders would have simply wrapped the house with 6 inches of rigid foam. But Southworth is an experienced timber-framer who prefers to use techniques with which he is familiar — and he's used SIPs for years.

Once the SIPs were attached to the framing and sealed at the seams with spray foam, the house already had a pretty decent thermal envelope. But Southworth and Rosenbaum weren’t done. The next step was to fill the 2x6 stud walls with closed-cell spray polyurethane foam, bringing the R-value of the walls up to R-52. The rafters were sprayed with foam until the roof totaled R-73, while the basement walls were sprayed to achieve R-42. The basement floor was insulated with R-25 of rigid foam.

All of the existing windows were replaced with triple-glazed fiberglass windows from Thermotech. Although Rosenbaum tried to talk Bindley into reducing the area of north-facing glass, she didn’t want to give up her dramatic lake view — so most of the home’s glazingWhen referring to windows or doors, the transparent or translucent layer that transmits light. High-performance glazing may include multiple layers of glass or plastic, low-e coatings, and low-conductivity gas fill. still faces north.

PassivhausA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates.-tight
Taping the exterior sheathing and spraying the interior with polyurethane foam created a very tight building envelope. Rosenbaum used a theatrical fog machine to track down a few stubborn leakage paths.

A pre-retrofit blower door test put the home’s air leakage rate at 4,000 cfm at 50 Pascals. After retrofit work was complete, a second blower-door testTest used to determine a home’s airtightness: a powerful fan is mounted in an exterior door opening and used to pressurize or depressurize the house. By measuring the force needed to maintain a certain pressure difference, a measure of the home’s airtightness can be determined. Operating the blower door also exaggerates air leakage and permits a weatherization contractor to find and seal those leakage areas. showed that the house was now Passivhaus-tight, with a leakage rate of only 330 cfm at 50 Pascals.

What kind of heat pump is most cost-effective?
The house has two heat sources: a wood stove and a water-to-water ground-source heat pump. The in-floor hydronic distribution system uses 95°F water circulating through PEXCross-linked polyethylene. Specialized type of polyethylene plastic that is strengthened by chemical bonds formed in addition to the usual bonds in the polymerization process. PEX is used primarily as tubing for hot- and cold-water distribution and radiant-floor heating. tubing. Since the water temperature is significantly lower than the temperature for some radiant floors — especially staple-up systems, which sometimes require 130°F or 140°F water — the heat pump's efficiency is much higher than it would be if it needed to raise the water to a higher temperature.

Ductless minisplit air-source heat pumps are much less expensive than ground-source heat pumps (GSHPs). Although a ductless minisplit requires a little more electricity to operate than a GSHP, a net-zero-energy house can provide the necessary electricity by specifying a somewhat larger PV array than would be needed for a GSHP. The cost of the extra PV modules is generally much less than the incremental cost of a GSHP compared to a ductless minisplit unit.

When asked why he specified a GSHP rather than a ductless minisplit, Rosenbaum identified two main reasons:

  • The limited area available for the PV array favored a heating system that used as little electricity as possible.
  • Japanese ductless minisplits rated for below-zero outdoor temperatures were not available in the U.S. when the Bindley project was under construction.

“Japanese minisplit units are getting better all the time, and they cost much less than a ground-source heat pump,” said Rosenbaum. “I predict that the ground-source heat pump industry will be eviscerated by the Japanese minisplits.”

Since domestic hot water needs to be at a higher temperature than the water circulating through the radiant floor, the domestic hot water system is entirely separate from the space heating system. The two roof-mounted solar thermal collectors are connected to two hot water storage tanks; backup heat is provided by an electric resistance element.

True net-zero performance
Utility bills confirm that in 2009, Bindley’s renovated house produced 1,732 kWh more electricity than it used. The extra electricity more than balanced the small amount of firewood (0.2 cord) that Bindley burned. That means that the Bindley house is one of only a handful of U.S. homes able to document 12 months of net-zero-energy performance.

Several factors contributed to the home’s performance, including:

  • The home’s exceptional thermal envelope.
  • The fact that Bindley covers her windows with movable R-7 foam-filled insulation panels at night.
  • The fact that the home is only occupied for about half the year.

Although Bindley sends more energy to the grid than she consumes, she still pays electric bills of $21.41 a month; that’s the minimum fee collected by the local utility, regardless of usage.

Getting to net-zero isn't cheap
Now that the U.S. Department of Energy is informing builders to prepare for a transition to zero-energy design and construction standards, it’s worth contemplating the steepness of the road ahead.

Bindley’s house is an exciting example of elegant engineering, but it cost an arm and a leg. Her insulation package cost $110,000; her PV array cost $60,000; her windows cost $37,000; her Warmboard subflooring cost $20,000. I was unable to obtain cost figures for other major components, including the ground-source heat pump (which may have cost upwards of $30,000) and the solar thermal system (which probably cost at least $10,000).

“Depending on how you crunch the numbers, the house cost between $350 and $400 a square foot,” said Southworth. In other words, Bindley’s deep-energy retrofit cost at least $1,190,000.

“The material choices were expensive,” Southworth explained. “Every decision we made was the most expensive option.” According to Rosenbaum, “The energy package could have been done for less money if we had used less spray foam.”

Convergent evolution
Bindley loves her new home. “I once lived in a 1970s house that was very drafty,” said Bindley. “This house is a pure delight in the wintertime, because it is invitingly warm and the air quality is so good. The air is moist and there are no drafts.”

One striking lesson from the Bindley job: if you’re aiming to build a net-zero-energy home in a cold climate, your envelope is going to end up looking like a Passivhaus envelope. Although some writers have contrasted the Passivhaus design approach with the net-zero-energy approach, in fact the two design approaches show signs of convergent evolution.

To get to the stringent net-zero-energy goal, you need Passivhaus levels of airtightness and Passivhaus levels of insulation — at least if you expect to fit all of the necessary PV modules on your roof.

Another lesson: if you’re aiming for net-zero energy, renovation may cost more than new construction.

A dream job
For energy nerds, the Bindley job is likely to represent the very archetype, the exemplar, the Platonic ideal of the perfect energy-retrofit job. Jane Bindley didn’t want to build a mansion; she just wanted to turn her 1978 ranch into a zero-energy home, and she had the budget to make it happen.

“Jane Bindley is an amazing person,” said Rosenbaum. “She would show up with coolers full of food and drinks for the workers — with more food than even the construction guys could eat.”

Southworth also remembers the job-site meals. “She would come every Thursday and make lunch for us, using ingredients from Whole Foods,” said Southworth. “She was wonderful.” Southworth also noted that Bindley, a physical therapist, “was always dragging guys off and giving them a massage.”

MORE INFORMATION AND PHOTOS: A True Net-Zero Gut Rehab, New England-Style

Last week’s blog: “Best Construction Details for Deep-Energy Retrofits”


Tags: , , , , , , ,

Image Credits:

  1. Ben Southworth
  2. Jane Bindley
  3. Heather Burkham
  4. Fletcher Manley
1.
Fri, 05/14/2010 - 08:26

Thank you, Martin, for a
by Marc Rosenbaum

Helpful? 0

Thank you, Martin, for a thorough treatment of this project. One clarification — although the house does not have full-time occupancy, two things make it similar to a full-time house. One is that the first year I had Jane keep the thermostat at comfort temperatures, and even now, it's best with low-temperature radiant floors to not use a deep temperature setback; and two, Jane has a large family and when the house is occupied there could be a lot of people there — one of the rooms is full of bunk beds :-)


2.
Fri, 05/14/2010 - 10:11

After Pictures
by Armando Cobo

Helpful? 0

Interesting approach, thanks for sharing. Is there a way to see more after pictures?


3.
Fri, 05/14/2010 - 10:26

"After" photos
by Martin Holladay, GBA Advisor

Helpful? -1

Armando,
I'm expecting to receive some more photos from Ben Southworth soon. Right now I don't have the photos you request. As soon as they're available, I'll post them to this blog.


4.
Fri, 05/14/2010 - 11:33

Basement insulation
by Kyle

Helpful? 0

Nice post Martin.

This is more of a question for Marc Rosenbaum if he comes back to the post. I was wondering about Marc's decision making process regarding the insulation of the basement. R-40 is very high and would most likely increase the number of freeze/thaw cycles experienced by the concrete. What was the mitigation strategy (leaving an unexposed area at the top of the wall for example) that was applied here? A discussion of assessing risk to basement walls when doing an insulation job with closed cell foam would be helpful.


5.
Fri, 05/14/2010 - 12:21

Is cold concrete at risk?
by Martin Holladay, GBA Advisor

Helpful? 0

Kyle,
I'm not aware of any study that shows that interior basement insulation damages a concrete foundation. After all, think about all of the outbuildings, sheds and unheated barns with poured concrete crawl space or basement foundations — as long as the footings are below frost depth, these foundations are not generally damaged by cold weather.


6.
Fri, 05/14/2010 - 12:28

Taped Sheathing Joints
by Brett Moyer

Helpful? -1

With closed cell spray foam in the stud cavities, is it necessary to tape the exterior sheathing joints? Perhaps at the rim joist area, but for the rest of the wall?
Just trying to figure out where to save money...


7.
Fri, 05/14/2010 - 12:38

Kyle - no issues that I know
by Marc Rosenbaum

Helpful? 0

Kyle - no issues that I know of with concrete, as Martin has responded.
Brett - belt and suspenders on this project, because there's a fixed energy budget, and we needed it to get really tight. We're making buildings under 1 ACH50 by taping the sheathing. Spray foam helps but there are plenty of places the foam doesn't get to so it alone won't easily get you to a really tight building.


8.
Fri, 05/14/2010 - 13:10

While we are on the Subject...
by Brett Moyer

Helpful? 0

Marc,
Did you seal the roof deck joints as well?
And it appears in one the posted pictures that you used a primer (wet areas around the taped joints) before you applied the Grace Vycor strips.
What did you use?


9.
Fri, 05/14/2010 - 13:24

re: Thanks Martin
by Ben Southworth

Helpful? -1

Martin, this is a great article! Brett, we used a Grace primer that Marc recommended to us. I still have a couple of gallons if you want to buy it from me! The reason I still have it is that we are now using Zip wall peel-and-stick wherever possible because of the excellent adhesion. Obviously on windows and doors the Grace is a little more robust especially with fasteners, but for seams it is all Zip tape without primer now.


10.
Fri, 05/14/2010 - 14:01

Cost
by Brett Moyer

Helpful? -1

Thank you for the response Ben.
How much did you spend to tape the sheathing joints (walls only)?
I am trying to calculate the amount of tape in linear feet needed for wall joints on a 3,000-ish square foot home.


11.
Fri, 05/14/2010 - 14:10

One more thing
by Brett Moyer

Helpful? 0

And when you say you are now using Zip wall peel and stick, are you using this tape on regular OSB sheathing?


12.
Fri, 05/14/2010 - 14:43

Interior vs exterior foundation insulation
by patric

Helpful? 1

Given the no holds barred approach to insulation in this project, I wonder why the decision to insulate from inside was taken. a similarly airtight construction could have been achieved with polyisocyanurate or type IX rigid insulation. The added benefit of thermal mass inside the building could have provided some advantages. I suppose costs of excavation could have eliminated this as an option (although given the overall budget I'm not so sure...). Curious. Nice post.


13.
Fri, 05/14/2010 - 14:49

More Info
by Armando Cobo

Helpful? 0

Marc,
I've done a few gut rehabs to very low HERS scores, however I'm still intrgued why you selected to use SIPS other than you are more comfortable with it. Did you do a cost analisys with other sytems or methods. Can you please elaborate? Forgive me if I'm asking too much, I do fing this job interesting, but too many questions left out.


14.
Fri, 05/14/2010 - 14:50

Questions...
by Ed Welch

Helpful? 0

Thanks for the article Martin. A good example of an unlimited budget, net zero home

Just a few questions:

1. Curious about the radiant floor system choice. I thought that was generally a inefficient choice in very tight homes. Maybe with the GSHP, that is the only option....although I thought that you could convert that to hydronic air system. But then you have the problem of installing a duct system that does not penetrate the thermal envelope, exhaust ,etc

2. You said that the client "covers her windows with movable R-7 foam-filled insulation panels at night." Never heard of such a thing. Would love some explanation.

3. A 7.5 Kw PV system....that is a huge system. I thought the solar exposure was minimal? How many panels is that? Approximate square footage? Was it installed somewhere away from the structure? $60,000 costs...is that the actual costs....or does that include any rebates?

Thanks


15.
Fri, 05/14/2010 - 14:51

refrase...
by Armando Cobo

Helpful? -1

... to many answers left out. I think Martin just gave us a teaser... :-))


16.
Fri, 05/14/2010 - 15:04

Reply to Armando
by Martin Holladay, GBA Advisor

Helpful? -1

Armando,
It was Ben Southworth, not Marc Rosenbaum, who preferred using SIPs to rigid foam. Southworth is a timber-framer who has a lot of experience with SIPs.

Here's one advantage to SIPs (at least for the roof): if you're doing a chainsaw retrofit, it's easier to recreate the rake and eave overhangs with SIPs than it is to tack on framing made of 2-bys.


17.
Fri, 05/14/2010 - 15:08

Reply to Ed
by Martin Holladay, GBA Advisor

Helpful? -1

Ed,
1. The Warmboard subfloor allowed the use of low-temperature water. That decision made the GSHP much more efficient.

2. You've never heard of movable nighttime window insulation panels? Ed, you must be a young guy. They were all the rage back in the 1970s, when the hippies and solar fanatics (I was one of them) were building experimental low-energy houses. Most people got tired of the twice-a-day chore pretty quickly.

3. No PV rebates were available in New Hampshire when this house was built, so $60,000 is the full cost and the net cost. It's not a huge system for a net-zero-energy house — in fact it's on the low side. Try to do better! I don't think you can sharpen your pencil any better than Marc Rosenbaum.

Solar exposure was not minimal; it was actually pretty good, with just a little wintertime shading. Wintertime shading doesn't matter too much. You don't make much electricity in New Hampshire in the winter anyway.


18.
Fri, 05/14/2010 - 15:11

Reply to Armando's other post
by Martin Holladay, GBA Advisor

Helpful? -2

Armando,
Just a teaser? Maybe. Some of my editors think my blogs are too long ... yet it seems I'm leaving some readers hungry for more details. I can't satisfy everybody — except that I'm happy to answer follow-up questions (thereby lengthening my blog....)


19.
Fri, 05/14/2010 - 16:32

SIPs Walls
by Armando Cobo

Helpful? 0

When you said, “the SIPs were attached to the framing…” as in a “floating wall”? No saddle footings? How were they attached? What type of final cladding? I’m looking forward to the final pics.


20.
Fri, 05/14/2010 - 17:23

PV calculations...
by Ed Welch

Helpful? -1

Martin,

I was not doubting Marc's PV calculations. I have 18 PV panels on my roof for a 2.5 Kw system in sunny CA. It just seemed like a large surface area would be needed for a 7.5 Kw system, probably more southward facing rooftop than even a 3500 square foot home has available. But maybe not?

And hey, I actually am not that young, but maybe younger than you.....but obviously, a little under-informed about such labor intensive insulating devices.


21.
Fri, 05/14/2010 - 17:34

SIP attachment details
by Martin Holladay, GBA Advisor

Helpful? 0

Armando,
I have just posted a detail (Image #5) the shows how the wall SIPs were attached to the existing house.


22.
Fri, 05/14/2010 - 17:43

SIP Attachment
by Armando Cobo

Helpful? 1

That's pretty cool. I could have used this technique several years a go. I used a saddle footing and we framed a wall next to the existing wall. The footing part was a pain. This is a good alternative.


23.
Fri, 05/14/2010 - 22:47

Thermal Bridge?
by John Brooks

Helpful? 0

Is the steel L Bracket continuous or is it a series of short brackets?
Either way it ...Is it not a significant thermal short circuit from the rim joist to the outside?


24.
Sat, 05/15/2010 - 05:13

Thermal short circuit?
by Martin Holladay, GBA Advisor

Helpful? 0

John,
Most people use the terms "thermal bridge" or "thermal short circuit" to refer to a building component that conducts heat from the interior conditioned space to the exterior. But the steel L bracket you are referring to conducts heat from the exterior to the exterior — it's hardly a "thermal short circuit."

The bracket is nowhere near the interior of the building or the conditioned space. The interior side of the rim joist is massively insulated with closed-cell spray polyurethane foam.


25.
Sat, 05/15/2010 - 08:00

Perhaps "Not-so-Bad"
by John Brooks

Helpful? -2

If the steel angle is not continuous then it seems to be "not-so-bad"

If it is continuous ... then what makes it any different from the "bad" example in the Clint Easwood anology in Lstiburek's paper
http://www.buildingscience.com/documents/insights/bsi-005-a-bridge-too-far

The interior of the rim joist does "appear" to be massively insulated in the illustration.
What if you take a section cut thru the floor joists instead of thru the cavity?
Cavity insulation alone at the rim joist does not address thermal bridging....Eh?

The outsulation at the rim joist seems to be "bypassed" by the highly conductive steel.


26.
Sat, 05/15/2010 - 09:37

Ventilation?
by Mike

Helpful? 0

Wondering what ventilation systems were used on this project.; both IAQ and roof ventilation, etc. used?


27.
Sat, 05/15/2010 - 10:32

Ventilation
by Martin Holladay, GBA Advisor

Helpful? 0

Mike,
Check the specs: mechanical ventilation is provided by a Renewaire energy-recovery ventilator.

Since the roofing is standing-seam metal over SIPs, I don't believe there is any roof cavity ventilation.


28.
Sat, 05/15/2010 - 10:44

Clint Eastwood thermal bridge
by Martin Holladay, GBA Advisor

Helpful? 0

John,
Joe's "Clint Eastwood" examples -- the bad and the ugly -- show continuous steel brackets continuously attached to a concrete slab at room temperature.

I think it's a stretch to say this is the same as a steel bracket which, every 16 or 24 inches, is adjacent to a narrow section of wood sheathing contacting a narrow 1 1/2-inch-wide area of framing that is in contact with room-temperature air about 7 or 9 inches back from the bracket, where the floor joist finally emerges from the foam.


29.
Sat, 05/15/2010 - 14:12

So ... the steel is not continuous
by John Brooks

Helpful? -1

Martin,
I agree that if this is a series of small brackets and not a continuous steel angle....
It is not-so-bad
It was just not clear from the illustration.
Are there any photos of this detail?


30.
Mon, 05/17/2010 - 16:49

New image -- the electric bill
by Martin Holladay, GBA Advisor

Helpful? -1

I have just posted a copy of one of Jane Bindley's recent electric bills. Her electricity usage is zero zero zero zero zero zero ....


31.
Mon, 05/17/2010 - 20:52

new definition of "mansion"
by pam

Helpful? 1

Wow, this is an amazing post. The level of detail is terrific - and the story really demonstrates the investment required to get to net zero. Not to diminish this effort, truly, I think we Americans are going to have to come to terms that in our new future, a 3,400 s.f. house that costs $1.19 million to retrofit -- will be known as a mansion. Or, do you think that over time, the costs will come down by a factor of 10 so that we can truly afford this kind of retrofit?


32.
Mon, 05/17/2010 - 22:25

Pam
by Armando Cobo

Helpful? 1

This is NOT a typical net-zero remodel. There are mamy, many 1,500-2,000 sf net-zero homes built to reasonable costs (±$30K-$50k) in NM, AZ and CA. You do not have to spend $1MM to get there. For what I can tell, her major costs to net-zero were around ±$300K or 25%-35% of the entire cost; which is typical to the up-costs of a net-zero home. We don't know how many other amenities and finishes she had installed in this project.


33.
Tue, 05/18/2010 - 04:59

Response to Pam and Armando
by Martin Holladay, GBA Advisor

Helpful? -2

Pam,
Although Armando is correct that most of the cost of this retrofit is not attributable to energy improvements, the cost to bring the house to net-zero performance was nevertheless breathtaking. I don't think the cost of this type of retrofit is ever going to come down by a factor of 10.

The fact is, builders interested in superinsulation retrofits have been performing this type of work since the early 1980s. We know the costs, and they are very high.

Armando: I'm aware of fewer than 10 homes in the US that have documented 12 months of net-zero energy performance. Almost all of them have PV systems ranging in size from 6 kW to 10 kW. (The exception is the David Pill house in Charlotte, Vermont, which has a wind turbine.)

For net-zero-energy performance, you're going to pay $42,000 to $70,000 just for the PV array. That doesn't cover envelope improvements.

Please provide more details on a house with only $30,000 of incremental cost that can demonstrate 12 months of net-zero-energy performance. Until I see more information, count me a skeptic.


34.
Tue, 05/18/2010 - 06:24

Which Half of the Year?
by John Brooks

Helpful? -2

Martin,
Do you know which half of the year the home is mostly occupied?
Is it a weekend retreat or a summer home?
Were the windows covered with insulated panels every night AND during the unoccupied half of the year?


35.
Tue, 05/18/2010 - 08:20

Response to John
by Martin Holladay, GBA Advisor

Helpful? -1

John,
The house is occupied three or four days a week, year round.

The windows are covered at night during the winter, but not during the summer. I imagine that the north windows are insulated (night and day) when the home is unoccupied during the winter, but I'm not sure.


36.
Tue, 05/18/2010 - 10:14

Affordable Net-zero
by Armando Cobo

Helpful? 1

Martin,
I've been in many presentations at green building conferences and events by ConSol and the Davis Group in CA, Artistic Homes in NM, John Wesley Miller in Tucson, BSC, Steve Winter's group, DOE, the Building America and ORNL have demonstrated homes around the country they've been working on affordable NZs for years. Even our buddy Peter did many presentations several years a go about affordable NZs in his BSC days and after. The UCF in FL, they've been working on NZs for a long time, at one time they had a website you could look in real time all their data. I'm sure contacting all of them would be happy to give you details.


37.
Tue, 05/18/2010 - 10:44

ConSol, Davis Group, Artistic Homes, John Wesley Miller...
by Martin Holladay, GBA Advisor

Helpful? -1

Armando,
None of the builders or researchers you list have made a net-zero energy home (mind you, I insist on 12 months of documented net-zero performance -- no firewood, no unaccounted for natural gas) that I am aware of. Correct me if I'm wrong by giving me the address of the home and the name of the responsible builder or researcher.

Moreover, if they have done it, I'm sure that the incremental cost was way more than $30,000 ...


38.
Tue, 05/18/2010 - 14:06

Affordable net-zero
by Pam

Helpful? 0

Thank you, Martin and Armando, for your responses. I would be really interested in anywhere you could point me that would document how to get to net zero -- in the most affordable way possible. I have this thing about "marginal rate of utility" of each dollar spent being a factor. That is, I am very cognizant of payback times and effective use of our collective (often: incentivized) spending to get at the problem as effectively as possible. I have read... and it kind of makes sense to me... that money is a proxy for carbon. That is, the low-hanging (inexpensive) fruit can be the most... fruitful. That said, I recognize that LCA is really likely the barometer. Anyway, I diverge. Re: affordable net-zero, I am looking for the specific details to get there today. I have been looking and looking online. So far, this website is the best I can find. But I still cannot find detailed "how to's." To be sure, there seem to have been great strides in products in the past year. But I having a devil of a time piecing it all together. Thank you!


39.
Tue, 05/18/2010 - 14:20

Response to Pam
by Martin Holladay, GBA Advisor

Helpful? -1

Pam,
You may be interested in reading two blogs that cover the topic of net-zero energy design:
"Equipment Versus Envelope"

"Thinking About Net-Zero Energy"

Here's the basic method: choose a good energy modeling program and run the simulations with many iterations of the house. Each iteration will need to be costed out, at least roughly.

Then you get to compare the energy performance of the different iterations. What happens if you add $5,000 more insulation to the attic? Is the performance better or worse than a house with $5,000 of additional PV modules?

What happens if you switch from double to triple glazing? Is the $10,000 incremental cost worthwhile?

NREL's BeOPT program (not yet widely available) sounds useful. But really, a good designer needs to become comfortable running these energy simulations and costing out the various construction options. Sometimes you have to just sharpen your pencil and do the math.


40.
Tue, 05/18/2010 - 14:32

Thank you
by Pam

Helpful? 0

Thank you, Martin. I'm a newbie here as you can surely tell. Your other blog posts - on super insulation and the energy efficiency pyramid are exactly what I am looking for, too. I've been online searching for about 10 days and finally landed here -- exactly where I wanted to be. Many thanks!


41.
Wed, 05/19/2010 - 15:09

Wow
by Charles Shade

Helpful? -1

Interesting article. Not for the average homeowner. Good things to take from the retrofit but overall this is at the top of the buying pyramid for both existing and new. Glad to know someone's got money.


42.
Wed, 05/19/2010 - 15:26

Excellent coverage
by Craig Savage

Helpful? -1

Well done, Martin.
A very informative and interesting article.
From 80,000 ft, we are at an early stage in the evolution of Net-Zero construction techniques and technologies, and more importantly -- demand.
Costs will come down and energy prices will rise...


43.
Wed, 05/19/2010 - 16:40

Response to Charles -- about the project cost
by Martin Holladay, GBA Advisor

Helpful? 0

Charles,
Here's another way to look at this project's cost. Assuming that the project cost $1,190,000, how else could the money have been spent?

Let's say that no energy retrofit work was performed. But perhaps Jane Bindley still wanted to spruce the place up. (Perhaps the 1970s shag carpeting and avacado appliances had to go.) So let's provide a budget that is 50% of the original budget to upgrade the interior finishes. That's $595,000 -- enough to make the interior spiffy -- very spiffy.

Remember, we haven't improved the energy performance of the house yet. Instead, we take the remainder of the original project budget -- the other $595,000 -- and invest it in a long-term investment that yields 4% interest. How much does that nest egg generate? Well, it generates $23,800 a year -- forever.

Do you think that $23,800 per year is enough to pay the energy bills on a ranch house? I think it probably is.

Just food for thought.


44.
Wed, 05/19/2010 - 18:41

PPT on this home
by Carmela

Helpful? 1

See PPT on this home at: http://www.affordablecomfort.org/ Look under ACI Initiatives, then Thousand Home Challenge, then case studies (4th or 5th link down the page).


45.
Wed, 05/19/2010 - 20:11

Another investment
by Dan Kolbert

Helpful? 1

Of course it's hard to make the financial argument. But hopefully the lessons we learn from projects like this will help push things along, will help us make the goals more affordable.


46.
Wed, 05/19/2010 - 20:48

Net zero
by John

Helpful? 0

Nice article for an unlimited budget. The insulation package could have been done much less expensive and still achieve good R values. 4 inches of foam on the outside and flash and batt on the inside would get the walls to 45 or so. This also helps with the water plane. Spray foam the ceilings to 7 inches provides a good air seal and R 49, which is in the new 2009 energy code. The basement insulation in my view is overdone. I think what we need to understand is that air sealing is more important than insulation values. If we approached a retrofit from the air sealing point of view and was on a budget, we would be sure to air seal first and then insulate the best we can. PV systems have to be sized to the use, however its not a good idea to oversize a system in NH as putting excess energy on the grid is not paid.


47.
Thu, 05/20/2010 - 06:33

Thanks Carmela for the ACI link
by John Brooks

Helpful? -1

Kudos to Southworth and Rosenbaum for doing what they could with what they were dealt.

It seems to me that the will of the homeowner may have been the component that drove the price tag off the scale.
It looks like Marc Rosenbaum "campaigned" to reduce the sliding glass doors and window area.....
Homeowner did not budge.
No wonder the levels of insulation and the price sound so ridiculous.

Bindley threw a lot of money at this but did not set a good example for others.


48.
Mon, 05/24/2010 - 15:31

Cost of Net Zero
by Quint David

Helpful? 1

Getting a home as efficient as possible is the first step... and then building the power plant is the second and very expensive next step. Making sure the homeowner doesn't install the $25 beer fridge from 1979 in the garage that makes the home not net zero is the 3rd step.

Education is everything!

On another note the different energy modeling programs give different opinions on how to estimate the near-zero for a building.... I feel that modeling pv output is much easier than modeling average person-habits and energy use within a building... but basing expensive decisions off the numbers can be problematic when we cant decide on which numbers to use!

Check out this presentation comparing some energy modeling tools... depending on which one you choose your home can have a very different 'estimated' energy use!

http://www.bgbg.org/resources/Documents/SB_Modeling_Software_Presentatio...


49.
Mon, 05/24/2010 - 15:49

Response to Quint
by Martin Holladay, GBA Advisor

Helpful? 1

Quint,
An interesting presentation -- thanks for the link.


50.
Wed, 05/26/2010 - 12:23

Mechanical System
by Steve Dodd

Helpful? -1

If the building envelope was built to a PassivHaus standard, why was such an expensive mechanical system chosen? One of the big arguments for spending money on the envelope is to save money on mechanical systems, especially with PassivHaus. Were the large expanses of north facing glass a determining factor?


Register for a free account and join the conversation


Get a free account and join the conversation!
Become a GBA PRO!