
Happy Halloween! (or Christmas, based on the most prominent displays right now at Walmart)
This month, let’s take a look at a subject I’ve been studying for a while: The State of Massachusetts Stretch Code. Have you heard of it? A government website explains it is called the Stretch Code because: “It’s a stretch between the existing Base Code and a more energy efficient building code.”
Well, the new code certainly is a stretch. In my view, it stretches the limits of common sense; it stretches people’s patience; and it most definitely stretches the size of the construction budget.
The newest version of the Mass. Stretch Code went into effect last year, and has been adopted by many communities in the Commonwealth, with more and more adopting it every month.
Here are a few things the new Stretch Code requires:
New and renovated buildings must include the electrical wiring/service needed to provide Electric Vehicle (EV) charging stations, including for at least 20% of the parking spaces available at commercial and multi-family buildings.
If gas-fired appliances are part of the HVAC design (boilers, furnaces, etc.), the project must include the infrastructure needed to convert to all-electric HVAC equipment in the future (heat pumps, radiant, etc.).
Energy Recovery Ventilators must achieve 70% total efficiency (sensible & latent) for both winter and summer designs, instead of the previous requirement, 50% total efficiency.
A different government website offered this take: “The Stretch Code aims to result in cost-effective construction that is more energy-efficient than what is built to the base energy code.”
Well, I’m sure it’s more energy efficient. But is it cost effective? Hmm, I’m skeptical.
Here at Melia Associates LLC, we don’t sell electrical equipment or heat pumps. But you don’t have to be an expert in those fields to understand that multiple EV charging stations and extra infrastructure for future use, along with designing a project twice (once with the gas boilers and a second design with all-electric equipment), can get quite expensive.
We do sell and understand Energy Recovery Ventilators (ERVs). I’d like to devote the rest of this blog to relaying what we’ve learned during the past 12 months.
First, to achieve the new 70% total efficiency goal, a desiccant wheel-type ERV unit typically needs to be one size larger than usual. This adds cost and requires a larger equipment footprint. For enthalpic core-type ERVs, such as RenewAire’s product line, often the unit needs to be two or three sizes larger!
Enthalpic core-type ERVs do an excellent job of transferring sensible heat, and a fairly good job of transferring latent heat (moisture). It is a fact that desiccant wheel-type units ERVs have noticeably better latent heat performance. But here are a few other things to consider:
Wheel-type ERVs have significantly more maintenance requirements than core-type units. Plus the wheel units have a lot more moving parts.
Over time, as the desiccant chemical wears off the wheel’s fins, the latent performance is reduced significantly. This does not happen with core-type units, as there is no chemical treatment on the core’s membrane.
Wheel-type units require frost control measures, since the wheel can start to freeze up when the outdoor temperature reaches the low teens above zero (Fahrenheit). RenewAire’s core does not have frost concerns unless two conditions are present at the same time: the outdoor temp must be minus-10 F or colder; and the indoor humidity must be 40% RH or higher. In our 20 years experience with RenewAire’s product line here in New England, we have never had a frost issue.
If a core-type ERV has 74% total effectiveness in the winter and 60% total effectiveness in the summer, that is still pretty darn good. And yet, it does not meet the new Stretch Code.
In one example where we crunched the numbers, a core-type ERV doing a mere 500 CFM, with the summer total efficiency at 60%, would cause the building owner to pay approximately 45 cents per day extra for the electric bill in the summer. To achieve the 70% goal, the owner would have purchase a larger ERV unit, with an additional install cost of $4840. So, the payback period for the larger, more efficient unit is a mere 120 years!
So, a key aim of the Stretch Code, according to the government website, is “cost-effective construction”? Yeah, sure. And the Red Sox are going to win the World Series later this month.
Learning about the Mass. Stretch Code during the past year has been one of those situations where the more you learn, the more you realize how much you don’t know. So, I freely admit my knowledge of the Stretch Code is, in many ways, surfacy and anecdotal.
Therefore, if you have any insights or information about the Stretch Code that would be helpful, please feel free to send me an email. If I receive some important updates, I will include those details in the future.
If most of your projects are in Connecticut, don’t dismiss this issue. Conn. often adopts codes that are in effect in Mass. and New York. Word is, the folks who call the shots here in Conn. are planning to adopt the requirements of the Mass. Stretch Code soon.
One final anecdotal story: we’ve heard from consulting engineers in Mass. that more than a few construction projects were cancelled this past year because the new Stretch Code added over 30% to the original construction budget. Yikes! That’s not insignificant.
The Stretch Code is more spooky than a Halloween horror film marathon (at least for me).
Enjoy trick-or-treating, and stay safe!
Bill Dunn, Engineering Sales, Melia Associates LLC 860-290-6969, bdunn@meliaassociates.com