Does a Passive House Use 90 Percent Less Energy?

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Does a Passive House Use 90 Percent Less Energy?

Examining an oft-repeated claim about Passive House energy savings

Posted on Apr 14 2017 by Martin Holladay
prime

Longtime readers of GBAGreenBuildingAdvisor.com know that I get frustrated by exaggerated energy savings claims. A glaring example is the statement that “a Passive HouseA 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. building uses 90% less energy than a conventional building.” A variation on this claim: “A Passive House building uses 90% less energy than a code-minimum building.”

It doesn’t, of course. The oft-repeated falsehood is based on a boast made by Wolfgang Feist in the 1990s. Back then, Feist claimed that a new Passivhaus residence needed 90% less energy for space heating than a “conventional” residence in Germany. (It's important to remember that space heating energy is just one small part of the energy-use pie.) The “conventional” residence that Feist was talking about was an average German home, not a new house meeting modern code standards. (Many German homes are decades, or even centuries, old.)

These days, Dr. Feist and the Passivhaus Institut are usually more careful in their statements than many of their enthusiastic followers. That said, it’s easy to find a Passivhaus Institut document online that includes the boast, without any qualifications about space heating or the age of the housing stock that is used for comparison. Here are two sentences from a Passivhaus Institut press release published in December 2015: “Feist built the world’s first Passive House almost 25 years ago. Still today, this terraced house in Darmstadt (Germany) consumes about 90 percent less energy than conventional buildings.”

As I said, it doesn’t. Let’s peel the onion and figure out why.

What two homes should we compare?

Let’s say that a young couple has money in the bank and wants to build a new energy-efficient home. The couple is weighing the added cost of meeting the Passive House standard (either the European standard or the new PHIUS climate-specific standards).

This hypothetical couple needs to keep two facts in mind:

  • They shouldn’t compare the predicted Passive House energy bills to those of an “average” house. Anyone thinking of building a new house should instead compare the proposed Passive House residence with a new code-minimum house. After all, no one is legally allowed to build a house with the same specifications as an average American house. Building codes are more stringent now than they were when most U.S. homes were built.
  • They need to keep claims about heating energy use in perspective. Heating energy use only makes up a small segment of total residential energy use.

New code-minimum homes don’t use a lot of energy

The most important fact undermining the “90% less energy” claim is that new code-minimum homes don’t use much energy. Why? Codes have gotten a lot more stringent during the last few years.


CLAIMS FOUND ON THE WEB

Inhabitat: “The Palatine passive home in Seattle uses 90% less energy than required by standard building code while providing a modern, comfortable living space."

Green Builder Media: “The result is a home that uses 90% less energy than a comparable 2,400 SF home built to today’s ‘code minimum’ standards.”

Sage Condos: “Passive Houses are ultra-energy efficient buildings that require only 10% of the energy used in a standard home or building.”

Sprarta Capital: "The energy savings in Passive Homes are achieved by using special energy efficient building components and a high-quality ventilation system. ... They are expected to use 90 percent less energy than a typical house."

Daniel Buck Construction: "Passive House construction gives you a home that uses 90 percent less energy than standard home construction at affordable building costs."

A&R Solar: “The German Passive House design standard requires buildings to use 90 percent less energy than code requirements.”

Dwell.com: “He describes with excitement how the house ‘substantially exceeds the standard energy code’ and notes with pride that the house will use 90 percent less energy than its neighbors consume.”

National Geographic web site: “No furnaces are needed, because they're projected to use up to 90 percent less energy than a typical house.”


I’m going to focus on the U.S., where the “90% less energy” claim is alive and well among Passive House adherents. (To read some examples of the claim, see the sidebar at left.)

To delve into this issue, I needed a good source of information on the energy used for new code-compliant homes. I found such a source online: the “Residential Energy & Cost Savings Analysis” documents prepared by the U.S. Department of Energy. These documents were prepared to determine the savings attributable to proposed energy code changes.

If you click the link in the paragraph above, you’ll come to a page with links to most U.S. states. (California, Oregon, and Washington state aren’t included, because these states have oddball energy codes.) If you click the name of a state you are interested in, you can find out the modeled energy use of a new code-compliant home. This modeled home is assumed to have 2,376 square feet of conditioned floor area. (More details on the modeled home are available on this web page.)

The modeling is fairly sophisticated. Its heating appliances and fuel prices are state-specific; for example, some states have an average electricity rate of 11 cents per kWh, while other states have an average electricity rate of 16 cents per kWh. The annual energy use figures include heating, ventilation, air conditioning, domestic hot water, and lighting, but (as far as I can tell) the figures exclude plug loads.

RESNET software assumes that residential plug loads (excluding lighting) average 4,500 kWh per year for the average U.S. household. In order to account for plug loads in the table below, I’ve added the cost of 4,500 kWh (for plug loads) to the total energy costs listed in the “Residential Energy & Cost Savings Analysis” documents cited above.

Here’s what we learn from this table:

  • Most new code-compliant homes have relatively low energy bills.
  • Energy costs for space heating represent less than 40% of total residential energy costs for most U.S. households.

Passive house data

I reached out to several people, including Katrin Klingenberg, the founder of PHIUS, requesting monitored energy use data for single-family Passive House residences. Klingenberg responded by email, “We have a PhD on the job who has collected measured data for all projects in the [PHIUS] data base (for those who responded to the request). The data is being analyzed right now and I believe the project is supposed to be done by the end of May. That’s when it will be available.” I’m eager to see the data; for the time being, however, we’ll all have to be patient.

In the meantime, I found five single-family Passive House residences in the U.S. with published estimates or monitored data for annual energy use. The data are presented in the table below.

Here are the sources for the energy use data or energy use predictions used to create the table:

Next, I calculated the estimated annual residential energy cost (including the cost per square foot) for a new code-compliant home in each of the four states under consideration. The annual energy cost that I calculated ranges from $1,710 in Virginia to $2,295 in Massachusetts. The annual energy cost per square foot ranges from 71.9 cents per square foot in Virginia to 96.7 cents in Massachusetts.

To see if these numbers pass the smell test, I compared them to published data from the 2009 Residential Energy Consumption Survey (RECS) published by the U.S. Energy Information Administration. According to the 2009 RECS, the average residential energy cost per year is $2,024, or $1.03 per s.f. It’s only logical that a new home complying with the 2015 IECC would have a somewhat lower energy bill, so my numbers pass the smell test.

Yes, the method of analysis is imperfect

The table above includes only five homes. That’s a very small sample. I’d be delighted if the sample were larger, and I invite GBA readers with monitored energy use to share their data with GBA readers. I’m especially interesting in learning whether any U.S. Passive House uses 90% less energy than a new code-minimum house of the same size.

The five homes may not be representative, of course. My assumptions about the energy bills for a typical code-minimum house can be criticized and improved. I’m aware of all the imperfections of my method of comparison. But it’s as good a comparison as I’m able to make until better data appear.

The ballpark calculations support my premise. Of the five Passive House residences I looked at, the best performing house (the Jason and Stephanie Specht house) used 54% less energy than a code-minimum house. That’s impressive. Bravo.

The house with the worst performance (the New American Foursquare house) used only 24% less energy than a code-minimum house.

So I think that it’s fair to say that a Passive House residence in the U.S. will use between 24% and 54% less energy than a new code-minimum house. That’s good, but it’s not 90% less. So please — let’s finally bury the 90% claim.

Why bring this topic up?

In a recent letter to the editor published in Fine Homebuilding, a reader named Sarah Cobb wrote, “Some of us build Passive Houses because it’s a phenomenal technical challenge and because it’s reassuring to know that our energy costs will always be a tenth of most of the homes built today.”

Fine Homebuilding published my response to Sarah Cobb, in which I noted that “the argument that your energy costs are a tenth of most of the homes built today is based on a myth.” My response then outlined the argument that is presented in more detail here.

My published comments brought a strong response on Twitter from Andrew Michler (whose Colorado Passive House was described in a GBA article by Scott Gibson). Michler tweeted, “It is painful to read Martin Holladay’s selective and biased interpretation of Passive House. Flat out misrepresents its energy and costs.”

When I saw Michler’s tweet, I wasn’t sure what I had written that pained him. So I asked him, and he responded, “FHB May response.”

I look forward to more data on this issue, from Andrew Michler or others, so that we can all get a good handle on a basic question: How much lower are the energy bills of Americans who live in a Passive House than Americans who live in a new code-minimum house?

Martin Holladay’s previous blog: “Two Views of Double-Stud Walls.”

Click here to follow Martin Holladay on Twitter.


Tags: , ,

Image Credits:

  1. Image #1: Martin Holladay

1.
Apr 14, 2017 3:29 PM ET

Edited Apr 14, 2017 3:31 PM ET.

For additional data, my pretty good house in Maine
by stephen sheehy

In our first full year, we used about 9500 kwh. House is all electric. Conditioned area is about 1650 square feet of interior space. House hit Passivhaus air tightness, R-70 ceiling, R-42 walls, R-16 under slab, triple pane Intus windows. Resistance water heater. Hot tub in unconditioned, but insulated room, probably adds quite a bit to load. We keep heat from minisplits at around 70-72° and use A/C rarely.
PV produced about 8000 kwh, so out of pocket energy cost was only $335 for the year.
If enough people provide real life data, we'll have some useful info to support (or not) Martin's point.


2.
Apr 14, 2017 4:35 PM ET

Edited Apr 14, 2017 6:50 PM ET.

Why be annoyed?
by Malcolm Taylor

I've asked posters here who are contemplating going the Passive House route why they want to pursue accreditation and got a few different answers, from wanting to show they were part of a community, to getting predicable results from their build.

I don't see why these motives, or a myriad of others are a problem - any more than deciding to build a Pretty Good or code minimum house - as long as they are based on a clear-eyed understanding of that the results will be. So what's to get annoyed about in Martin's analysis?

Is there a morality component to the discussion that is being avoided under all the talk of data? For some reason whenever Passive House comes up there seems to be a subtext of "you are either for us or against us" that enters into the discussion. It reminds me of the many splinter groups of marxists who would fight among themselves in the entrance of my Montreal college back in the '70s while the world passed them by.

Martin is an Energy Nerd. He gets upset by bad data wherever he sees it. If Passive House purged itself of these claims I bet he wouldn't spend as much time picking holes in it.


3.
Apr 15, 2017 4:56 AM ET

Edited Apr 15, 2017 4:58 AM ET.

Response to Stephen Sheehy
by Martin Holladay

Stephen,
Thanks for your data -- it's appreciated.

With the caveat that Passive House adherents are likely to ignore your house (since it's not a certified Passive House), here's how your numbers look: The cost of your annual energy use of 9,500 kWh is $1,330 (at a statewide average electricity cost of $0.14/kWh). That translates into 80.6 cents per square foot.

A code minimum house in Maine uses $1.02 per square foot, so your house uses 21% less energy than a code minimum house.

The three relevant tables are shown below.

.

Stephen Sheehy house energy savings.jpg


4.
Apr 15, 2017 6:25 AM ET

Response to Malcolm Taylor
by Martin Holladay

Malcolm,
Thanks for your comments. Like you, I think that the Passive House approach is admirable. The problem isn't the Passive House approach; it's simply the exaggerated claims.

-- Martin Holladay


5.
Apr 15, 2017 8:00 AM ET

Response to Martin
by stephen sheehy

In Maine, communities with more than 4000 residents are required to adhere to the state building code, which incorporates the 2009 IBC and 2009 IEEC. Smaller communities may, but aren't required to, adopt either or both codes. My little town hasn't adopted either.

I'm not surprised that my house only used 21% less energy than the code minimum house. I suspect most of the advantage is in heating cost, since most other electricity use employs typical energy star rated appliances which are widely used. As I mentioned in my earlier comment, the hot tub probably uses a good deal of power.


6.
Apr 15, 2017 11:49 AM ET

Edited Apr 15, 2017 11:49 AM ET.

Stephen
by Malcolm Taylor

Remembering the measures you took to make you make your house efficient, it's obvious that you are a profligate and irresponsible inhabitant and that occupant behaviour is to blame for the lack of a 90% energy savings. I hope you, your wife and the cat are suitably chastened.


7.
Apr 15, 2017 12:26 PM ET

My other favorite PH claim
by Kye Ford

My other favorite Passive House claim is that "it doesn't cost anymore to build a Passive House or "we are building PH for only 5% more than a standard code built house." I heard this claim over and over during my PHIUS training. I naturally took this with a grain of salt, and whenever I asked for more exact numbers as to build costs I was always given some sort of whitewash answer.

If you want to build a PH certified home that's fine, but to say it isn't going to cost more than a code built home is ridiculous.


8.
Apr 15, 2017 2:33 PM ET

Edited Apr 15, 2017 2:35 PM ET.

BEOpt
by Ethan T ; Climate Zone 5A ; ~6000HDD

I have found BEOpt, which is available for free (for now :/) from the Dept of Energy to be very useful in comparing PH measures to code construction, and to try to find sweet spots (perhaps leading to Pretty Good House levels of insulation and glazing). I have not accurately input material costs yet, but that can even better help make intelligent decisions on terms of where to put one's hard earned money. What I don't know is how accurate the BEOpt calculations are, and I don't really have the expertise to guage that. Any insight into whether I can trust BEOpt output would be very helpful.


9.
Apr 15, 2017 2:44 PM ET

If only
by Brian Knight

It seems most new residential in the Midwest and South hasn't caught up with current efficiency minimums. Comparing to code-minimum makes sense for readers of this site but some questionable 90% claims could be true when compared to the majority of homes being built, which do not seem to fit the current energy models. Help bring the bottom up while keeping the top from floating away.


10.
Apr 15, 2017 8:00 PM ET

Reply to Malcolm
by stephen sheehy

While my wife and I try our best, the cat adamantly refuses to be reasonable and when no one is looking, turns up the thermostat, runs the dishwasher empty except for his dish and insists on clean beds every hour. The dog is too intimidated by the cat to be of any help. The cat thinks Passivhaus means he can lay around all day and do nothing.


11.
Apr 16, 2017 5:26 AM ET

Edited Apr 16, 2017 5:28 AM ET.

Response to Brian Knight (Comment #9)
by Martin Holladay

Brian,
Your point -- that "the majority of homes being built ... do not seem to fit the current energy models" or minimum code requirements -- is an important one.

The Passivhaus approach (and the PHIUS approach) include quality assurance methods -- for example, mandatory blower-door testing -- which add value to the resulting house. That's worth something, especially considering the low level of code compliance observed in most of the U.S.

Anyone building a custom home probably cares about quality assurance. That said, I imagine that there are less expensive approaches (for example, the Energy Star approach) that also include quality assurance inspections and blower door testing.

-- Martin Holladay


12.
Apr 16, 2017 12:11 PM ET

Quality assurance and costs
by Charlie Sullivan

I agree with Martin's comment #11 that that biggest advantage of a certification program is quality assurance. When I embarked on my pretty good retrofit, I was pretty confident that between the GC's expertise and mine, we knew how to do things right. Of course we didn't, but even if we had known, making sure it actually gets done as specified is exhausting. Having an external standard helps make sure you have a complete checklist of things to consider, and it helps to prevent disputes about doing things right from seeming as personal.

I agree with Kye that most Passive House projects are probably a lot more than 5% over the cost of conventional construction. Some of that has to do with the rigid nature of the energy targets--once you'd done all the reasonable things to get close, the standard sometimes forces you do take extreme measures that don't really make sense. That's unfortunate, because just before that point, you really do have opportunities for real savings through installing smaller HVAC systems that help offset the cost of a better envelope.

But it's important to also keep in mind that there are lots of custom houses that cost double what standard construction costs without any energy savings at all. It's easy for costs to escalate quickly when there are mistakes in design or project management, and when any aspects, whether they have anything to do with energy or not, stray outside of what the contractors are experienced in.

Marc Rosenbaum had a blog post here a few years ago talking about "handprint" vs. "footprint":
http://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/reflections-b...
The concept, roughly speaking, is to consider the handprint, meaning what you or your project can do to move the world towards lower energy consumption, not just what minimizes your own consumption (footprint). The handprint of a Passive House project might include educating contractors and getting visitors to your house interested in low-energy building. For a prospective homeowner, the best opportunity might be to hire a team who has successfully built a passive house, and ask them to instead build a pretty good house.

The handprint of a passive house project might justify the expense, even when the energy savings doesn't. Perhaps the exaggeration of benefits is done in an attempt to enlarge the handprint, but I think it's better to be honest and realistic about the challenges as well as the benefits.


13.
Apr 16, 2017 12:43 PM ET

Brian Knight has a point
by Antonio Oliver

I think a most important point was made by Brian Knight in comment 9. Comparing to code minimum only scratches the surface. Where I grew up (rural Mississippi) there effectively was no code--(Sheathing, what sheathing? You mean siding? I have seen this with my own eyes.). And in many places, I bet "no code" is still the case. Another point to be made is that not all states have adopted IRC 2015. I'm pretty certain that my local Virginia county has not--code is county by county. So good start Martin, but for the next iteration, I'd like to see you pin the code adopted in localities to the houses being built "code minimum" in that place.


14.
Apr 16, 2017 12:47 PM ET

Data point
by Charlie Sullivan

Martin, if you want pretty good data points too, our pretty good retrofit of a ~2200 sq. foot house in central NH has used 6800 kWh in the last year with electricity as the only energy input. That year includes 4-5 months during which we weren't quite finished. The lack of construction work and the better envelope should reduce the consumption for those months this year.

Occupied by two people. No cat, so that probably accounts for most of the difference relative to Steve's numbers. Or else it's the occasional visits from a pair of dogs. They are pretty good, but not at all passive, so there's definitely some additional BTU input when they are here.


15.
Apr 16, 2017 5:07 PM ET

Antonio
by Malcolm Taylor

You are no doubt right, although I guess that begs the question as to whether it might be more important from an energy conservation perspective to enforce the new codes than try and increase the number of Passive Houses.

Martin was quite specific though (and this is borne out by the quotes in the sidebar) that he is responding to claims that Passive Houses use 90% less energy that those built to a "code minimum".


16.
Apr 17, 2017 6:42 AM ET

Response to Malcolm Taylor
by Martin Holladay

Malcolm,
I agree with your point about code enforcement. It's easy to criticize the construction industry in North America -- I do it all the time -- but the solution to the problems in our industry isn't necessarily the Passive House approach.

If code mandates aren't being enforced, we need to come up with strategies (as home buyers or as communities) to address the enforcement problem.

If we need better quality assurance programs and blower-door targets, let's come up with ways to implement them. All of these issues can be addressed without necessarily adopting the Passive House approach.

-- Martin Holladay


17.
Apr 17, 2017 7:40 PM ET

Edited Apr 18, 2017 12:43 PM ET.

Aim High
by Joe Dwyer

Thanks for this comparative analysis. It seems that the best Passive Homes do set a very high bar, which is a good thing. Here is my data from last year:

2,160 sf, IN (4A), 9,903 kWh, 55 cents/sf. ($.12/kWh)

2015 IECC comparison for S. IN:

2,400 sf (two story), IN (4A), 14,142 kWh, 71 cents/sf

Details of our home- Split-level (split foyer/bi-level), circa 1982, tract home, R-70 in attic, 2x4 walls with fiberglass, brick siding with air gap, newish double pane vinyl windows, all electric, 13 SEER/8.5 HSPF split 2.5 ton heat pump, ducts inside between floors, 50 g. electric resistance water heater.

We compare very well with 2015 IECC, although our lower level 4 feet below grade is more efficient than two story by design.

Next on our list- HP water heater (split or relocate tank to garage), DC replacement ceiling fans, metal roof (with air gap?), new split heat pump when current one fails.

Finally, our usage jumped 10% last year when our older son moved back in. Now four living here.


18.
Apr 18, 2017 12:41 PM ET

4,500 kWh Plug Load?
by Joe Dwyer

Looking over our electricity use last year, it was 2.4K kWh for "plug use," and this includes electric stove/range and electric clothes dryer. 4.5K seems way too high, at least for the person who is efficiency minded and might have a Passive House, pretty good house, or improved older house.

Now if comparing all homes, it sounds right. Our utility tells us we use app. 60% less electricity than 100 comparably sized all electric homes in our area.


19.
Apr 18, 2017 12:43 PM ET

Edited Apr 18, 2017 12:44 PM ET.

@ Joe Dwyer
by Brian Croston

Joe, you are a great example of what can be achieved in existing construction by just getting back to basics and making incremental improvements. Talking about R60 walls and R90 ceilings is fun, but there are many lessons to be learned from a common sense approach.

Even with R-9 (R13 fiberglass in 16"o.c. framing) walls, after adding the HP water heater and higher efficiency HP mini split, your consumption will be close to 50% of the norm. That's awesome! Are you already using LED lighting, E.S. appliances, and eliminating phantom loads as well?


20.
Apr 18, 2017 12:54 PM ET

Edited Apr 25, 2017 8:27 AM ET.

Plug load numbers
by Martin Holladay

Joe,
You're right that plug load energy use ranges widely in the U.S. Plug loads are a growing piece of the residential energy use pie, for several reasons -- heating energy use is dropping, and Americans' love of electronic gadgets is growing.

That said, one family can easily have a plug load budget that is 3 or 4 times higher than the family next door.

I'm interested to see Katrin Klingenberg's data on Passive House energy use, especially the plug load data. It's quite possible that the average family living in a Passive House has smaller-than-average plug loads. If I had to speculate, I might reckon that people who buy a Passive House aren't typical Americans -- they're interested in energy efficiency. So one possible explanation for lower energy loads is that this type of house appeals to a certain demographic.

If the Passive House standard ever became mandated by building codes -- unlikely, but this is a hypothetical exercise -- the energy savings associated with my "certain demographic" explanation would evaporate.

To be clear, I'm speculating here.

-- Martin Holladay


21.
Apr 18, 2017 1:14 PM ET

Edited Apr 18, 2017 5:43 PM ET.

@ Brian Croston
by Joe Dwyer

Thanks. It's been an incremental approach over many years.

Yes, all phantom loads are gone and it's mostly LED lighting except for a few old CFLs still in use. Appliances are all HE, including a new ventless heat pump clothes dryer installed in late December. Whirlpool lowered the price by adding a non hybrid version and we jumped in. It works fine, except that it does take longer for heavy towels, etc. It's not a big deal and the heat stays inside with no outside make up air like with a standard vented dryer. Dryer is in the lower level of house.

Our "builders grade" home always amazes me with the corners they cut to save a buck. For example, the original 90 watt Broan ceiling ventilation fan in the bathroom recently started groaning so I replaced it with a new Broan that uses only 20 watts. Unfortunately, they used 3" vent pipe instead of the standard 4". Off to the store to find an adapter and tin snips were used in the opened up ceiling cavity to make the old 3" pipe fit to length with 4" industry standard fan air outlet.

Some pain and sweat always seem necessary to get incremental efficiency with an older home!


22.
Apr 19, 2017 5:01 PM ET

PH uses 90% less energy
by Anders Lewendal

I agree and have met a few energy academics that think every house in the US should meet PH standards. I think one in particular lives in a 10 ACH older home. Since I finished a PH custom home last year I can report to her that the construction costs were easily 15% higher than an equal code compliant home. My client asked me to build a PH home with a .35 ACH even though he knew he was going well beyond diminishing returns. Comfort was one of his reasons. I enjoyed the process.

If someone wanted to save the world from CO2 and could build a PH I would recommend building a PGH and sealing up grannies house next door and adding some attic insulation to it. Most folks do not understand how important diminishing returns are to the energy equation.


23.
Apr 19, 2017 5:28 PM ET

Metered comparison to 40,000+ homes
by Jonathan Beers

I hope this post is helps rather than muddies the waters. Attached are two annotated screen shots of how our 1938 bungalow compares to 40,000+ single family homes in the Madison, WI area. The screen shots compare our metered gas and electric consumption for the 12 previous months to metered data from the 40,000+ homes. (Data is updated daily).

To make the comparison fit Martin's example, I entered 2376 square feet as the heated area, rather than the actual 1164 square feet of our small home. (Martin wrote: "This modeled home is assumed to have 2,376 square feet of conditioned floor area).

I also chose to compare our 1938 home to homes constructed since 2000 to better match Martin's goal of comparing to new code compliant homes. No modeling here, just metered data. The square footage and date of construction for the 40,000+ comparison homes comes from the City Assessor's data.

GasComparison.jpg ElectricComparison.jpg


24.
Apr 20, 2017 9:40 AM ET

Edited Apr 20, 2017 9:59 AM ET.

Response to Jonathan Beers
by Martin Holladay

Jonathan,
I'm not sure that the data you have provided add much to the discussion, but for what it's worth, here is my analysis:

A new code-minimum home measuring 2,376 s.f. in Wisconsin (assuming compliance with the 2015 IECC) would have an average annual energy bill of $2,086.

It appears that the average 2,376 s.f. house in Madison uses 520 therms of natural gas a year for space heating (costing $578) and 9,300 kWh of electricity a year (costing $1,302) for a total annual energy bill of $1,880 -- less than my modeled average for a code-minimum house. (Note: I assumed 6,250 heating degree days.)

Conclusion: either Madison residents are energy misers (good for them), or the plug load assumptions I used for the code-minimum house are too high. Either way, I don't think your data alter my fundamental conclusion about the "90% less energy" claim made by some Passivhaus enthusiasts.

For what it's worth, your data closely match the 2009 RECS data for Wisconsin, shown in the bar graph below. (It looks like residential energy expenditures in Wisconsin total an average of about $1,900 per year).

-- Martin Holladay

2009 RECS data for Wisconsin.jpg


25.
Apr 20, 2017 11:05 AM ET

> he knew he was going well
by Jon R

> he knew he was going well beyond diminishing returns. Comfort was one of his reasons

There are comfort metrics, would be interesting to see this quantified. I'm pretty sure it's minor and easily offset with a little bit of thermostat adjustment.


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