Could an Energy Code Really Be So Simple?

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Energy codes have all kinds of requirements. You have to have certain R-values in walls, floors, and ceilings. Your windows have to have the right U-values and solar heat gain coefficients. The infiltration rate and duct leakage have to be measured and come in below a threshold for your climate zone. And then there are the different pathways for compliance: prescriptive, UA tradeoffs, performance, or HERS Index. But what if all you needed to do was to hit two numbers?

The Perfect Energy Code

Henry Gifford and Chris Benedict put on a little 10 minute, one-act play last year called The Perfect Energy Code (watch below), and they propose a dramatic simplification of the energy code in New York City. No more energy modeling. No more reference designs. No more prescriptive or performance paths. Just hit their two numbers with your design and you get your permit. Install the equipment you designed into the building and you get your certificate of occupancy (CO).

Simple enough for you? Watch the video to see what they say about it.

The only two numbers you need

The two numbers they put in their perfect energy code are described in this screenshot from the video:

perfect-energy-code-chris-benedict-henry-gifford

You design your building and specify the heating and cooling equipment you're going to use. Then divide the total input capacity of those systems by the square footage of the building. They give 15 BTU per hour per square foot for heating and 5 Watts per square foot as the thresholds for New York City.

For the nitpickers, yeah, those equations above shouldn't both have an x on the right. If the heating has to be less than x, the cooling would need to be less than y, but you get the point.

Each location would then have its own numbers for x and y. The colder the climate, the bigger the x would be. The hotter the climate, the bigger the y would be. It's a lot like the new climate-specific passive house standard from PHIUS in that way. Those numbers would also have to depend on what type of building it is. Supermarkets, hotels, schools, and homes have different needs and consumption patterns.

Their numbers are a kind of energy use intensity (EUI), which is the energy consumed by a building per square foot. Normally it's calculated for all energy used over the course of a year. Their numbers are based only on heating and cooling rather than all energy, and they use rated input energy rather than actual measured energy use.

Could it work?

It would definitely be simple. It also, as they say in the video, would eliminate a lot of the ways people game the system with energy modeling. Verifying compliance would be a breeze, too. So what are the downsides?

The designers of new buildings would still have to do some modeling to make sure they size their systems properly. They'd still have to make sure the building enclosure is well-insulated and airtight, as long as the x and y are low enough for the climate and building type. If the equipment specified turned out to be inadequate because of poor building design or installation problems, someone would have to pay to fix the problems.

Will people try to cheat? Probably. But with a simpler energy code, it would be harder to cheat, I think. What could they do? Install one system for the final inspection and then replace it with a bigger one after they get the CO? Try to have extra capacity hidden in the building somewhere and hope the inspector doesn't find it? Come in afterward and install mini-split heat pumps if there are problems? Certainly possible but not smart.

I think something like this really could work.

 

Related Articles

What's Your Energy Efficiency Number?  —  my article on EUI, with a spreadsheet calculator

I Use an Air Conditioner Sizing Rule of Thumb!  —  similar idea to Chris's and Henry's

Do You Know Your Building Science Climate Zone?

 

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Comments

Bill Southworth

Very interesting analysis and it fits in with our own observations. At Elecyr, we collected data from a wide variety of buildings, architects and various government data sets and looked for correlating data to solar insolation, energy use, life style, buidling efficiency, etc. We found that you could derive a very good estimate with just four data points - building efficiency estimated from leaky to passive, square footage, US state (some surprise here), and whether the house was "all electric"or used fossil fuel. Our calculator is at http://elecyr.com/solarcalculator. With the lower costs of solar panels, keeping design and installation costs down can add a lot of additional panels. Simplicity almost always pays off.

Cameron Taylor

Sounds interesting. Just one question; the hotter a climate is the higher the "y" value will be, and the colder a climate is the lower the "x" value will be. I get that. I'm curious how the "x" and "y" values are determined in the first place. Is it one where an "average" building (per construction type) is modeled and then energy consumption targets are encouraged to come in below that, such as the above equation suggests?

Thomas Peterson

I have always tried to push for the KISS (Keep It Simple Stupid) principle and this approach certainly follows that. I think that such a system could be developed and work with some fine tuning. I also like the fact that it is more performance based and leaves the energy efficient design and equipment performance to the professionals that are responsible for both design and performance delivery.

I also like the fact that it promotes a type of competition between designers to come up with better and better designs and systems.

I would totally support the adoption of such a clean approach for energy code compliance.

Armando

Until then, I continue to design my projects with a few basic requirements, HERS50, 1ACH50 & 1ton/1500sf; with mind to achieve DOE's ZERH program. How we get there is a compromise between the homeowners, the builder and I.

Armando

Well... thinking a bit more about it, how many times we design buildings with all the right numbers, get the building permit in a jiffy, but the quality of construction is not there? Maybe I'm a strong believer that testing keeps everyone honest!
Besides, what would we do with all those unemployed HERS Raters?

Tapani Talo

FOR NEW BUILDINGS, ROOFS R=80, WALLS R=40+, WINDOWS R=14 (SOUTHWALL GLASS)
BASEMENTS INSULATED BELOW GROUND INCLUDING SLAB R=25
GEO THERMAL HEATING AND COOLING THAT DOES NOT REQUIRE FRESH AIR TO FUNCTION - NEEDS TO BE MINIMAL AT THIS POINT
MY CLIENTS JUST LOVE THE COMFORT AND PRACTICALLY ZERO ENERGY UTILITY COSTS

Richard P

I am not sure it would be performance based even if enforced simply because energy performance is not really known until occupied, ideally over a few seasons. Having the client trying to enforce poor performance after the occupancy permits are issued is bound to fail unless the clients hire their own HERS inspectors before the closing date.

Tapani Talo

It is very well understood by all the engineers that I use but from experience these numbers that I use are fairly optimum. I do know that not many equipment specifiers are not used to well insulated structures, and there lies a problem as they over size these. geothermal suppliers are very well tuned to what is needed.

Bill Southworth

Very interesting analysis and it fits in with our own observations. At Elecyr, we collected data from a wide variety of buildings, architects and various government data sets and looked for correlating data to solar insolation, energy use, life style, buidling efficiency, etc. We found that you could derive a very good estimate with just four data points - building efficiency estimated from leaky to passive, square footage, US state (some surprise here), and whether the house was "all electric"or used fossil fuel. Our calculator is at http://elecyr.com/solarcalculator. With the lower costs of solar panels, keeping design and installation costs down can add a lot of additional panels. Simplicity almost always pays off.

Cameron Taylor

Sounds interesting. Just one question; the hotter a climate is the higher the "y" value will be, and the colder a climate is the lower the "x" value will be. I get that. I'm curious how the "x" and "y" values are determined in the first place. Is it one where an "average" building (per construction type) is modeled and then energy consumption targets are encouraged to come in below that, such as the above equation suggests?

Thomas Peterson

I have always tried to push for the KISS (Keep It Simple Stupid) principle and this approach certainly follows that. I think that such a system could be developed and work with some fine tuning. I also like the fact that it is more performance based and leaves the energy efficient design and equipment performance to the professionals that are responsible for both design and performance delivery.

I also like the fact that it promotes a type of competition between designers to come up with better and better designs and systems.

I would totally support the adoption of such a clean approach for energy code compliance.

Armando

Until then, I continue to design my projects with a few basic requirements, HERS50, 1ACH50 & 1ton/1500sf; with mind to achieve DOE's ZERH program. How we get there is a compromise between the homeowners, the builder and I.

Armando

Well... thinking a bit more about it, how many times we design buildings with all the right numbers, get the building permit in a jiffy, but the quality of construction is not there? Maybe I'm a strong believer that testing keeps everyone honest!
Besides, what would we do with all those unemployed HERS Raters?

Talbott W. Blake

Armando you are correct. Until there is more and better training of installers testing will always be a necessity.

Tapani Talo

FOR NEW BUILDINGS, ROOFS R=80, WALLS R=40+, WINDOWS R=14 (SOUTHWALL GLASS)
BASEMENTS INSULATED BELOW GROUND INCLUDING SLAB R=25
GEO THERMAL HEATING AND COOLING THAT DOES NOT REQUIRE FRESH AIR TO FUNCTION - NEEDS TO BE MINIMAL AT THIS POINT
MY CLIENTS JUST LOVE THE COMFORT AND PRACTICALLY ZERO ENERGY UTILITY COSTS

Talbott W. Blake

Armando you are correct. Until there is more and better training of installers testing will always be a necessity.

DCE

Heating and cooling at what comfort level (and I'm sure your discussions with Robert Bean enlightened you to the multi-faceted world of comfort)? At what location in the building? Since air tightness also affects indoor humidity levels (which is a large driver of perceived comfort), how is that factored in - especially in the "steamy states" where people run their AC to dehumidify, not just cool? I like the idea about "simple" but, as always, the devil is in the details.

Bill Peterson

Having the construction end of the project is just as important as the engineering without both the project will never be as be successful and provide the client the expected value.

Another observation is we have raters and inspectors that do not have the practical knowledge to actually provide guidance, looking at the little things and not seeing the big picture as the whole building just a very small portion, not the total building as a system.

Richard P

I am not sure it would be performance based even if enforced simply because energy performance is not really known until occupied, ideally over a few seasons. Having the client trying to enforce poor performance after the occupancy permits are issued is bound to fail unless the clients hire their own HERS inspectors before the closing date.

Tapani Talo

It is very well understood by all the engineers that I use but from experience these numbers that I use are fairly optimum. I do know that not many equipment specifiers are not used to well insulated structures, and there lies a problem as they over size these. geothermal suppliers are very well tuned to what is needed.

DCE

Heating and cooling at what comfort level (and I'm sure your discussions with Robert Bean enlightened you to the multi-faceted world of comfort)? At what location in the building? Since air tightness also affects indoor humidity levels (which is a large driver of perceived comfort), how is that factored in - especially in the "steamy states" where people run their AC to dehumidify, not just cool? I like the idea about "simple" but, as always, the devil is in the details.

Bill Peterson

Having the construction end of the project is just as important as the engineering without both the project will never be as be successful and provide the client the expected value.

Another observation is we have raters and inspectors that do not have the practical knowledge to actually provide guidance, looking at the little things and not seeing the big picture as the whole building just a very small portion, not the total building as a system.

David Butler

One advantage of this approach is the simplicity of making future improvements to the code. But I think the most important advantage is rather subtle... it would give general contractors a huge incentive to implement a robust QA regimen to avoid the comfort complaints and bad rep that would surely follow if as-built envelope falls short of modeled specs.

On the other hand, GC's might find it easier to pad themselves by going beyond the minimum specs indicated by the model (a good thing), but they would have no incentive to further downsize the equipment. In other words, there would be a perverse incentive ratchet up the envelope specs a bit and then install the largest hvac allowed by code.

Hmm...

David Butler

One advantage of this approach is the simplicity of making future improvements to the code. But I think the most important advantage is rather subtle... it would give general contractors a huge incentive to implement a robust QA regimen to avoid the comfort complaints and bad rep that would surely follow if as-built envelope falls short of modeled specs.

On the other hand, GC's might find it easier to pad themselves by going beyond the minimum specs indicated by the model (a good thing), but they would have no incentive to further downsize the equipment. In other words, there would be a perverse incentive ratchet up the envelope specs a bit and then install the largest hvac allowed by code.

Hmm...

Tapani Talo

I am afraid that in both counts we are against the grain. HVAC people have no clue what efficiency, and sizing is about, and they earn more with larger, so no incentive.
As to home sizes, builders and their subs go for the BIG, clients like BIg as it is about their status..
Until we have energy tax (allocated by how far from passive one goes) on houses and cars (anything less than 100 miles per gallon or eq) , nothing will change.

Ryan Shanahan

I like the simplicity of it but when it comes to a residential application I think it will unfairly reward larger homes. In the Earth Advantage home certification program we created a target energy consumption metric per number of bedrooms per climate in an attempt to drive overall consumption down and take home size seriously. Yes, this requires energy modeling but so does the suggested perfect system. At least I hope HVAC contractors aren't using the old rules of thumb to determine the heating and cooling system inputs!

Tapani Talo

I am afraid that in both counts we are against the grain. HVAC people have no clue what efficiency, and sizing is about, and they earn more with larger, so no incentive.
As to home sizes, builders and their subs go for the BIG, clients like BIg as it is about their status..
Until we have energy tax (allocated by how far from passive one goes) on houses and cars (anything less than 100 miles per gallon or eq) , nothing will change.

Dave

While I think this approach as merit, I forsee four difficulties here:

1) this could only be implemented for new construction buildings as alterations sometimes do not touch the envelope and/or HVAC systems. As time goes on, more projects are renovations rather than new construction meaning only a fraction of buildings would apply.
2) especially on the residential side of things at the moment, the industry is somewhat constrained by the limited number of small capacity heating and cooling systems. I.e. in a well designed apartment, are they going to have to resort to through only wall A/Cs or variable capacity systems?
3) significant support to non-energy savvy designers and builders would have to be implemented. What does a building look like that meets these standards? What has to be done to achieve this? And in so doing, you basically end up with the energy code.
4) through this method, a failure of energy efficiency results in a failure of human comfort after the Certificate of Occupancy has already been granted. The primary fix to a now existing building is to add greater capacity system so people are comfortable.

Ryan Shanahan

I like the simplicity of it but when it comes to a residential application I think it will unfairly reward larger homes. In the Earth Advantage home certification program we created a target energy consumption metric per number of bedrooms per climate in an attempt to drive overall consumption down and take home size seriously. Yes, this requires energy modeling but so does the suggested perfect system. At least I hope HVAC contractors aren't using the old rules of thumb to determine the heating and cooling system inputs!

Dave

While I think this approach as merit, I forsee four difficulties here:

1) this could only be implemented for new construction buildings as alterations sometimes do not touch the envelope and/or HVAC systems. As time goes on, more projects are renovations rather than new construction meaning only a fraction of buildings would apply.
2) especially on the residential side of things at the moment, the industry is somewhat constrained by the limited number of small capacity heating and cooling systems. I.e. in a well designed apartment, are they going to have to resort to through only wall A/Cs or variable capacity systems?
3) significant support to non-energy savvy designers and builders would have to be implemented. What does a building look like that meets these standards? What has to be done to achieve this? And in so doing, you basically end up with the energy code.
4) through this method, a failure of energy efficiency results in a failure of human comfort after the Certificate of Occupancy has already been granted. The primary fix to a now existing building is to add greater capacity system so people are comfortable.

WHN

I haven't heard Henry Giffords name since the 07'LEED report in the ASHREA mag. Here he is making sense in public again....

WHN

I haven't heard Henry Giffords name since the 07'LEED report in the ASHREA mag. Here he is making sense in public again....