Your Questions Answered: Modernizing Yesterday’s Buildings to Leverage Today’s HVAC Opportunities Webcast

A June 11 webcast highlighted the latest technologies to help engineers upgrade HVAC systems for their existing buildings. Here are the additional audience questions from the event.

By Consulting-Specifying Engineer June 28, 2024
Austin, Texas Skyline At Sunset

Modernizing commercial buildings can be challenging due to factors such as aging building automation technology, competing priorities, lack of funds and a shortage of skilled labor. Helping building clients optimize systems can yield significant benefits, in both financial and HVAC energy savings.

During a webcast on June 11, 2024, Modernizing Yesterday’s Buildings to Leverage Today’s Opportunities, presenters from Trane Commercial highlighted common HVAC system types from the past 50 years and explored retrofit and upgrade opportunities inclusive of the latest technologies to help engineers with their clients’ existing buildings.

Additional questions were answered by Sarah Hilden, HVAC systems applications engineer, Trane Commercial.

When converting a chiller to variable flow, wouldn’t it be better to put in a main bypass rather than leave several three-way valves to maintain minimum flow?

Answer: Yes, it would reduce additional flow, as bypass flow would only occur when required.  You certainly could, but space constraints may be an issue.

What do you do when the power goes out?

Answer: Many buildings have backup generators.

Do you recommend maintaining or installing a backup electric or gas heat source when converting to an air-source heat pump (ASHP) system for heating?

Answer: Many designers do, or they maintain existing boilers.

I’ve heard that low global warming potential (GWP) refrigerants are flammable. Is that true? What concerns do you have about safety associated with using these?

Answer: They are but the temperatures to ignite are very high, and they have a low probability of flame propagation.  ASHRAE Standard 15 -2022 includes new requirements for machinery rooms using A2L refrigerants and high-probability systems.

How can you calculate or estimate energy savings when changing the set points of your cooling and heating equipment?

Answer: An energy model could lend to this, or a simplified bin approach could leverage the performance gains over impacted hours.

Does the difference in efficiency between electric power plants and on-site take distribution losses into account?

Answer: Distribution losses were not considered in any coefficient of performance (COP) comparisons.

Did you cover the efficiencies of the variable refrigerant flow (VRF) systems?

Answer: I did not cover VRF in detail — just a mention.  I did state that they can operate to lower ambient temperatures.

Please, please, please, use the word ALTERATIVE energy (alternative methods to generate electrical power, heat energy, etc.). We are not renewing (renewable energy) anything, just using an alternative energy source through a different process. I wish I could reprogram the individual or individuals that “coined” that term “renewable.”

Answer: Point taken. The reference was in regard to renewable energy sources like photovoltaic (PV) and wind.

How it is possible to have COP that are superior to 1?

Answer: The use of heat pumps enables COPs of greater than 1.  Heat out divided by electric power in.

What new innovations do you see taking hold in the industry, and how can engineers stay on top of them?            ‘

Answer: Certainly, cold climate heat pumps and technology to make hotter fluid and air will be coming. Becoming an ASHRAE member or subscribing to technical publications is one way to stay on top of advancing technology.

Can you describe environment, social and governance (ESG) further? How can one quantify an ESG score in building designs? Who has authority when it comes to ESG scores? Can this authority negatively affect a building owner if not compliant?

Answer: ESG programs may be adopted by companies. There are several voluntary reporting programs and ratings systems that could sway investors, I suppose.

When a heat recovery coil is placed in the air pressure balancing exhaust, should it be placed ahead of or behind an enthalpy wheel or other heat recovery ventilators (HRV) and energy recovery ventilators (ERV) that may be present?

Answer: I would think more heat could be recovered by the coil if it was upstream, but it may be more efficient to let the wheel do the work directly.

Would you not consider envelope upgrades to be HIGH-COST, HIGH-RETURN? Depending on the building we are talking about, that will be a huge undertaking. I would say that making sure your envelope is up-to-date (i.e., meets current energy code) is a high-reward process.

Answer: Yes, apologies if that wasn’t clear from the slide or talk track. Discharge air temperature (DAT) reset = low effort, high reward. Building envelope = likely high effort, high reward. This is not a typical place to start.