Draft Scoping Plan Residential Building Shells

For over two years I have been reviewing New York’s Climate Leadership and Community Protection Act (Climate Act) primarily with respect to those aspects where I have a professional or personal interest in the impacts to me.  One of the topics that I have spent a lot of time on is residential electrification with an emphasis on home heating.  This article addresses the building shell requirements necessary to include when home heating is electrified. 

Everyone wants to do right by the environment to the extent that efforts will make a positive impact at an affordable level.  I have written extensively on implementation of New York’s Climate Act because I believe the ambitions for a zero-emissions economy embodied in the Climate Act outstrip available renewable technology such that it will do more harm than good.  The opinions expressed in this post do not reflect the position of any of my previous employers or any other company I have been associated with, these comments are mine alone.

Climate Act Background

The Climate Act establishes a “Net Zero” target (85% reduction and 15% offset of emissions) by 2050. The Climate Action Council is responsible for preparing the Scoping Plan that will “achieve the State’s bold clean energy and climate agenda”.  They were assisted by Advisory Panels who developed and presented strategies to the meet the goals to the Council.  Those strategies were used to develop the integration analysis prepared by the New York State Energy Research and Development Authority (NYSERDA) and its consultants that quantified the impact of the strategies.  That material was used to write Draft Scoping Plan that was released for public comment at the end of 2021. The Climate Action Council will revise the Draft Scoping Plan based on comments and other expert input in 2022 with the goal to finalize the Scoping Plan by the end of the year.

Last April Jim Shultz authored a Niagara Gazette commentary titled: Is New York state coming after our furnaces? that addressed a rumor that the Climate Act would ban gas furnaces.  I mention the article because he eloquently described the Draft Scoping Plan: “The plan is a true masterpiece in how to hide what is important under an avalanche of words designed to make people never want to read it.”  Nowhere is this more evident than in the documentation associated with residential electrification building shell requirements.

If you are interested in background information, in an article describing my interview with Susan Arbetter at Capital Tonight I gave an overview of heat pump technology and described building shells.  In the energy efficiency world, building shells refer to the insulation, infiltration, window treatments and ventilation components of the building.  I will focus on building shell requirements in the rest of this article.

Draft Scoping Plan Building Shells

The Draft Scoping Plan does not include a description of the building shell assumptions sufficient to differentiate between the reference, basic, and deep shell categories used in the Integration Analysis.  The primary reference for Draft Scoping Plan information related to building shells is Appendix G, Integration Analysis Technical Supplement Section I chapter 3.3 Sectoral Results – Buildings.  The following paragraph is the entire narrative description of building shells.

Building shell improvements (such as improved insulation, window treatments, or deep home retrofits) are modeled as reducing service demand for HVAC devices. Improvements to buildings incur costs but improve home and office comfort in addition to reducing energy bills. Two bundles of building shell improvements have been included: a basic shell upgrade and a deep shell upgrade. Basic and deep shell upgrades include a variety of measures focused on reducing energy use and increasing occupant comfort; these measures include, for example, varying levels of roof and wall insulation improvements, window treatments such as double or triple paned windows and infiltration improvements. Space heating demands are reduced by 27-44% with the basic shell package and 57-90% with the deep shell package, depending on building type. Air conditioning demands are reduced 14-27% with the basic shell package and 9-57% with the deep shell package. The total impact of building shell improvements on total HVAC service demand in buildings is a function of the market penetration of each package and distribution of building types. Building shell improvements include both retrofits and new construction, although all new construction in residential and commercial is assumed to be code-compliant and therefore has lower HVAC service demands relative to the existing building stock. E3 calculated the stock rollover of building shells with a 20-year lifetime to reflect improvements in new construction and opportunities for home retrofits.

In addition to the narrative description of building shells there is descriptive information in the supporting spreadsheets.  The Annex 1 Inputs Workbook spreadsheet, Tab: Bldg_Res Device Cost lists device costs for three categories of residential households: large multi-family, small multi-family and single family.  Costs are listed for the three types of building shell upgrades and for air source heat pumps, electric resistance backup heat, and ground source heat pumps.  I used this information to estimate total residential heating conversion costs for my comments on the Draft Scoping Plan.

In the Annex 2 Key-Drivers spreadsheet there are tabs with building shell metrics.  Scenarios 2-4 note that in 2020 there were a total of 8,301,996 residential buildings with 48,551 basic shell residences, 37,699 deep shell residences, and 8,215,747 reference shell residences.  There is no difference in the projected building shells for the three mitigation scenarios. For scenario 2 (tab S2_Building Shells) in 2050, the integration analysis projects 8,684,001 residences, with 5,714,918 basic shell residences, 2,285,000 deep shell residences and only 684,080 reference shell residences.  The following table lists the projected number of different types of building shells and the annual deployment rate.

A couple of points about this table.  Note that the number of building shells in the Reference Case differs from the mitigation scenarios in 2020.  Obviously, there should not be a difference.  I have no idea which set of numbers is correct.  The second point is that the mitigation scenario deployment rates are unrealistic between 2030 and 2040.  The total of the basic and deep shell conversions works out to over 1,250 building shell upgrades per day.

Practical Application

So much for the theory.  I live in a single-family residence heated with an efficient natural gas furnace.  In my opinion one of the disadvantages of heat pump technology is that the output heat is relatively low compared to a combustion source furnace.  The temperature at the register for a heat pump system is around 90oF whereas in my house the temperature is around 120oF.  My concern is that there are some cold rooms in my house even when the furnace is providing hot air despite my best attempts to adequately insulate and reduce air infiltration.  The worst problem is in the bedroom we added over the garage.  In order to determine what I would need to do to install an air source heat pump that would provide comfortable heat year-round I really needed an energy audit.

National Grid recently announced a Home Energy Savings Program in cooperation with the New York State Energy Research & Development Authority (NYSERDA) that included an assessment of energy use in homes that was open to customers in my county.  Figuring I had nothing to lose I requested an audit.  When I scheduled the home assessment, I said I was particularly interested in what I would have to do to install a heat pump.

I believe that National Grid has a contract with ICF to manage the Home Energy Savings Program.  ICF arranges for local heating, cooling and air quality contractors to provide the assessments themselves. I believe that National Grid and NYSERDA pay for the audit but I got the impression that the auditor could make a commission if equipment was sold.  The auditor assigned to do my assessment had a certification from the Building Performance Institute and knew his stuff.  Interestingly the fact that he was unfamiliar with the basic and deep shell terminology used in the Draft Scoping Plan suggests that the Plan’s authors were not certified by the Building Performance Institute.

Audit Results

The auditor and an intern working for the company spent two hours evaluating my house from top to bottom.  We talked about my concerns and needs and then they checked the outside of the home and the main floors, basement and attic interiors.  Because my primary concern was home heating, they concentrated on heat loads.  As has been the case for every aspect of the Climate Act I have evaluated closely, reality as explained by experts is different than the situation portrayed in the Integration Analysis.

Heat loads can be calculated two ways.  According to the auditor “About 90-95% of the industry is still in the stone age and sizes systems based primarily off square footage of the home… not actual heat loss or heat gain through insulation, windows, building material, volume of home, area of building envelope/shell areas, etc.”  The preferred alternative is to do an Air Conditioning Contractors of America “Manual J Calculation” or “Heat Load/Heat Gain Calculation”.  He explained that “This historically has been done manually, and since the computer age came about there are now Manual J software programs which are used to model homes and run the calculations for you based off different input data gathered from a home during an energy audit”. 

The auditor has found that about 90% of the homes he analyzes have drastically oversized heating equipment which he attributes to the older and less accurate heating load calcuations.  As a result, there are the following consequences: rapid cycling, reduced efficiency and system lifespan, and reduced comfort and adequate distribution because of the fan always cycling.  He said that sizing is even more important for condensing furnaces, heat pumps, and air-conditioners.  He has seen condensing furnaces (i.e. 92% efficient or better) with cracked heat exchangers after only 5 years because of these problems. 

He also explained that air conditioning systems work by removing moisture, so if they are oversized and rapidly cycle, they will not be removing enough moisture from the air at the correct rate at which the air is cooled.  Most people who complain of hot rooms in the home are told they need a bigger air conditioning unit.  This is counterintuitive and the wrong way to do it.  A bigger system means more airflow is needed, and if the ductwork sizing is not adjusted accordingly, the evaporation coil will freeze on the furnace and the system will shut down until it defrosts.  Another scenario is that with rapid cycles you end up with cold air but it is still humid… giving that clammy cold feel.  Or, the problem doesn’t change at all and the room still stays too hot because it is related to the amount of air getting to that room through a duct.  The duct size is the limiting factor because only large systems (100,000btu or higher) have larger blower motors that can move sufficient air. 

With regards to heat pumps, it is particularly important that the heat loads are calculated correctly.  If the heat pump is oversized you end up with the efficiency of basically resistant electric strip heat (baseboard electric heat).  He said that New York’s push for heat pumps is unsophisticated because the way the grants are designed it forces contractors to oversize the heat pumps.  Apparently, some heat pump brands might be okay if they are oversized.  He explained that:

Some efficiency will be lost if the system is oversized, however they can still run efficiently relative to oil, propane, natural gas, and don’t always end up running at the efficiency of basic strip electric resistant heat.  The most important thing with heat pumps is “turn down ratio”, aka what is the lowest heat output it can produce.  As long as the lowest heat output on a heat pump unit is still higher than the particular demand of a home on any day during any hour of the winter, it will still operate properly and efficiently.  Will some efficiency be lost still?  Yes, but not nearly as bad as if the turn down ratio is higher than the lowest heat requirement of the home as noted above.  A lot of installers don’t get this unfortunately.  Neither does New York State.  But we can still win battles against it all day-to-day through conversation.

There are other ACCA manuals: Manual S covers heating and cooling sizing and selection, Manual T is used to determine air distribution within the building, and Manual D supplements the other manuals to determine appropriate heating and cooling duct design.   The obvious point is that all this information is necessary to properly design a replacement building shell heating, ventilation, and air conditioning system.  If it is done wrong there will be serious problems.

Building Shell Definitions

In response to my question about the building shell the auditor could not respond.  He asked me and all I could do is point to the sparse Draft Scoping Plan documentation.  We agree that the documentation is insufficient for contractors to specify improvements necessary to meet the Plan definitions.  This section contains my best guess but there is an inconsistency with the Integration Analysis projections.  In a post in November 2020 I noted that you could see the variation in energy efficiency in my neighborhood by looking at early morning frost patterns.  Based on my crude analysis only 10% of the homes in my mid-60’s housing development appear to have large reduction potential, 50% could use improvements compared to the remaining 40% of homes that appeared to have well-insulated homes.  If the reference shell refers to a home with minimal insulation, then my best guess is that the reference shell would only be 10% of the existing stock in my neighborhood.

My November 2020  post also included the following overview slide of the residential housing sector profile of New York prepared by the New York State Energy Research and Development Authority (NYSERDA).  It was included in the Energy Efficiency and Housing panel presentation on October 16, 2020.  Note that “at least 22% of residences have under-insulated exterior walls and roof”.  This is another possible definition of the reference shell but that is inconsistent with the Integration Analysis  2020 housing stock estimates.

The auditor made the point that the industry does not use the Deep and Basic shell terminology defined in the Integration Analysis and Draft Scoping Plan.  Instead, there are industry standards of R-Value (R-49 for attic flats, for example).  However, that approach over simplifies the actual energy losses.  He explained that spray foam vs. attic flat cellulose/fiberglass batt R-Values are not an “apples to apples” comparison because the foam seals air infiltration too.

In our discussion he explained that one of the factors which differentiate “deep shell” work vs. “basic shell” work could be hitting the building airflow standard (BAS).  He said that NYSERDA requires their contractors to hit BAS for all retrofit jobs that are getting heat pump funding through low income NYSERDA grants.  He explained that this this is a problem because:

I have seen maybe two or three retrofitted homes in 10 years that have hit BAS when all industry standard R-Values in walls, basements, crawl spaces, attics, windows etc. are achieved.  However, there is some “gray” when calculating BAS, and it comes down to what you consider “conditioned space”.  If a basement is not heated with supply grills/supply ducts dedicated to the basement, by definition the basement is not considered “conditioned space” and therefore the volume of the basement is not included in the BAS (i.e. the BAS value for the entire home is lower, making it much harder to achieve on retrofit projects).  However, since there is by definition heat loss through the metal in ductwork (up to 10,000-15,000btu on average I have found which is defined in Manual J calculations as “duct loss”) then would this not latently be heating basements and crawl spaces?  This is what I have assumed when calculating my heat loads and BAS calculations.  I include the basement, insulated or not, and crawl spaces (only when insulated for crawl spaces due to vents, etc.) as conditioned space because they are being latently heated.  This makes the most sense to me.  In my experience I have seen most retrofitted homes meet BAS when including the basement as conditioned space. 

There is another complication. When running Manual J’s, I negate out the “duct loss” factor since in a basement the latent heat being “lost” is going directly into the basement and above grade walls anyway.  This 10,000-15,000btu “duct loss” is another “oversizing” issue when running Manual J’s.  Ultimately this means that out of the maybe 5% of companies out there running Manual J’s instead of sizing by house SQ FT. very few of that 5% are removing “duct loss” in their Manual J’s according to where the ducts actually are.  If they run through a vented crawl space or the run outside (or a non-air sealed/non spray foamed mobile home underbelly), I would consider that true “duct loss”.  A basement or unvented crawl space under a home is providing heat to the house.  If that is not done correctly the result is that the system will be over-sized. 

Also note that there is a reference to air leakage with respect to the Passive House standard in the NYSERDA slide.  My best guess is that “deep” building shell improvements are equivalent to the international standard for passive buildings. It includes the following measures:

There is an inconsistency in the building shell deployment table with respect to the 2020 distribution of building shell types concerning the relative distribution.  The Integration Analysis claims that about half a percent of the existing building stock meets the deep shell criteria.  If my guess that the Passive House criteria represent a deep shell, I think that would be consistent.  The problem arises with the reference shell.  Both my crude analysis or the NYSERDA 22% are under insulated criteria for the reference shell are far less than the Integration Analysis presumption that 99% of the residences in New York have reference shells in 2020. 

The definition problem is most acute between the reference and basic shells.  Apparently, the basic shell is something intermediate between meeting all the passive house criteria and being under insulated. Ideally what the energy contractors of the state and the authors of the Draft Scoping Plan need to do would be to define what constitutes the standards for each level of building shells based on the passive house measures.

There are some ramifications to the existing lack of specificity.  The Integration Analysis assumes energy and emission reductions based on the conversion from reference to basic and deep shells.  It appears that the analysis is not accounting for the large number of residences that have enough building shell upgrades beyond the reference shell that they should be considered basic shells.  Ignoring this means that the projected improvements in the Integration Analysis are far greater than can be reasonably expected.


Several months ago, I contacted the writer of a letter to the editor because he raised important points about building ventilation. He is an expert on ventilation analysis and energy efficiency and I asked him about the passive house resource ventilation requirement reference.  I asked what the reference to passive house ventilation with highly efficient heat recovery would entail.  He said that it referred to using an Energy Recovery Ventilator (ERV).

He explained that it is much easier to incorporate into an existing HVAC system than it sounds. They are not free, but “using one pays dividends in many cases as for health and human performance”.  Although he has dealt mostly with commercial units he mentioned that Panasonic has been advertising a new residential unit, the Intelli-balance 200 ERV that retails for around $2700.

The concept is simple:  Air is exhausted and as it goes through a heat exchanger in the ERV.  About 70% of the energy is transferred to the incoming air for either heating or cooling mode.  There are two fans (sometimes only one motor runs them both), filters to protect the heat exchanger, and the heat exchanger.

He said that “these amazing units were not available 40 years ago, or they were all metal and very expensive”.  He offered a few other tidbits:

  • ERVs use a small amount of electricity for a residence.
  • ERVs have one intake, one exhaust, one air supply and one return that gets exhausted.
  • ERVs are relatively quiet when properly installed.
  • ERVs recover about 70% of the energy from the exhaust air.
  • ERVs can be integrated into a home furnace in the winter because the ERV pre-warms the air significantly before it enters the mixing box where the full air flow goes into the furnace.  For example, 100 cfm of ERV air in mixes with 900 cfm of return air so the mix is nearly the same as ordinary return air.  This way the furnace heat exchanger is not being fed very cold air which can be harmful to a furnace not designed to heat air that is very cold.

He also explained that the ERV forces exchange of inflow and exhaust.  The ERV can adjust the air flow exchange so that a bathroom or kitchen exhaust brings in a little more air than you exhaust.  You do not want to create a negative pressure in the house especially where there are gas burning appliances.  It is possible to draw air away from the cooking, water heating or space heating if they do not have forced draft combustion as also do some furnaces. This is a concern when infiltration is minimized to the standards suggested in the Integration Analysis.  Furthermore, if you bring in a slightly more ERV air than is exhausted the house is then slightly pressurized so there are few to no drafts. 

Finally, he made the point that these building systems cannot be evaluated by just looking at one piece.  All the air into the house or commercial building needs to be accounted for.  All the appliances have to work together to control the air flows and pressures of the building.  It is not complicated, but does need attention.  The final heating ventilation and air conditioning recommendation he made is the need for residential humidifiers in our cold dry climate in the winter.  Dr Stephanie Taylor MD has shown that when space humidity is too dry it can increase the risk of colds, flu, and other respiratory ailments.

My Audit Results

The auditor explained what he thought would be needed for shell upgrades for a system that would make air source heat pumps a viable alternative for my home.  My furnace is over-sized and the duct work is under-sized for the existing system.  As noted above one of the big issues with the whole house heat pumps is that you need to change the ductwork to enable more air flow so I would need to replace a lot of the existing system.  My house would need to get more insulation and sealing at the sill of the basement wall.  I have installed a ceiling in most of the basement and that would have to be ripped out.  It may be that those costs are included in the Integration Analysis projections but due to the lack of documentation we don’t know for sure.

Relative to the added bedroom over our garage and he said those were notorious for heating and cooling problems.  In order to fix that he recommended a ductless heat pump at an approximate cost of $5300 but there is a National Grid grant of $500 so the cost would be $4800.  He did mention that there is a wait time for these systems and whole house heat pump systems are simply not available at this time. 

I did not request a quote for a whole house system.  Nonetheless he gave me some suggestions. Given the changes needed to the duct work the whole house system would be more expensive that the ductless systems.  His initial thought was that we would need four ductless heat pumps to do the whole house but it is not clear to me how that would work.  On the main floor a system at each end of the house would provide heat for that floor.  If there are two systems on the upper floor how is heat supposed to get into the other two bedrooms – sleep with the doors open?  The estimate of four system also does not include heat for the basement.

He admitted that converting to a air source heat pump could not save money compared to using natural gas and noted that given the state of my house upgrading insulation, windows and air infiltration would not ever pay back the investment either.   He said most of his clients that install heat pumps do it for environmental reasons.


I do not doubt that heat pump technology can work in New York State.  However, it is not simply a matter of swapping out a fossil-fired furnace for a heat pump and the potential for the conversion to be done improperly is high particularly given the tremendous rate of conversions envisioned in the Integration Analysis.  Clearly it is not just the heating system but the building shell needs revisions too.  Based on my discussions with these experts the air infiltration, inflow, and exhaust requirements are much higher priorities than I realized.  The Climate Action Council needs to be sure that the Final Scoping Plan adequately defines the building shell criteria so that experts in the field understand what the State claims is necessary for the different building shell types.  This is also crucial so that the projected energy savings and emission reductions are achieved.

Author: rogercaiazza

I am a meteorologist (BS and MS degrees), was certified as a consulting meteorologist and have worked in the air quality industry for over 40 years. I author two blogs. Environmental staff in any industry have to be pragmatic balancing risks and benefits and (https://pragmaticenvironmentalistofnewyork.blog/) reflects that outlook. The second blog addresses the New York State Reforming the Energy Vision initiative (https://reformingtheenergyvisioninconvenienttruths.wordpress.com). Any of my comments on the web or posts on my blogs are my opinion only. In no way do they reflect the position of any of my past employers or any company I was associated with.

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