Kelly: (00:06 )
welcome to buildings and beyond

Robb: (00:08 )
the podcast that explores how we can create a more sustainable built environment

Kelly: (00:13 )
by focusing on efficiency, accessibility and health.

Robb: (00:18 )
I’m Robb Aldrich

Kelly: (00:19 )
and I’m Kelly Westby. Around here when we think of air source heat pumps, We think of Robb Aldrich. He is a principal engineer and he’s been working at Steven winter associates since 2000, before that, he designed, installed and commissioned solar electric and solar thermal systems. But now he’s just mostly focused on researching new trends and technologies to make buildings more efficient. And we’ll get to hear a little bit today about his research on air source heat pumps. Welcome to buildings and beyond, Robb, it’s very good to have you here.

Robb: (00:54 )
Thank you very much. It’s been a while.

Kelly: (00:58 )
we are obviously going to talk about air source heat pumps and I guess my first question is why are we talking about air source heat pumps?

Robb: (01:07 )
Boy, so 20 years ago, like when I was in Grad school or just started Grad school, the electric heating was just anathema. It was the worst possible thing in the world. Because generating electricity only happened at like 30- 35% efficiency and you know, much, much more resource efficient to burn fuels in buildings to get the heat from them.

Kelly: (01:36 )
and that’s I think what our clients are saying to us now when we talk about air source heat pumps.

Robb: (01:40 )
Yeah. Yeah. It could very well be, but it was 10-15 years ago when I started looking at some of the specs of these, what was then, a new generation of air source heat pumps and saw some pretty staggering efficiencies at relatively cold temperatures and its kind of blew my mind. So I mean a pump, I guess people probably know what a heat pump is, but a heat pump uses a vapor compression cycle to move heat from one place to another from outdoors to indoors in the winter and then backwards in the summer, like your fridge moves heat from inside the fridge into your kitchen, this moves heat from outdoors to indoors to heat your home. And historically, heat pumps- air source heat pumps, which is what we’re talking about today, rather than ground source heat pumps or water source heat pumps, air source heat pumps have historically been used further south where it’s warmer. Because they don’t- they didn’t- used to perform very well at cold temperatures. So in Florida, lots of air source heat pumps, you know, when the temperature got down to 30ish degrees or whatever, they switched over to electric resistance. And that didn’t happen all that often. So it wasn’t really a big energy hit. But up here it would be a big energy hit.

Kelly: (03:01 )
we operate very often below that temperature

Robb: (03:04 )
below 30 degrees. Yeah. So this was something that fascinated me. I was kind of incredulous of the performance, you know, the rate of performance of these systems. So I was keeping an eye on it for, well, for the past 10 or 15 years and watching how the products evolved and really was interested to see if we could actually measure performance to see if they lived up to their hype, their ratings.

Kelly: (03:31 )
All right. Interesting. And maybe this is a step backwards, but that’s the lay the groundwork a little bit. Can you talk a little bit about the terminology that we use around water source heat or air source heat pumps and what the industry is calling things, and what you like to call things?

Robb: (03:47 )
Yeah, there’s unfortunately there’s lots of different terminology that people use and I don’t pretend to be the authority on it, but I try to be at least consistent myself and do what I hear most other people do when they talk about it. So a mini split is a term that you may hear a lot. And to me mini split means mini, small capacity, and split. So you have an outdoor unit and an indoor unit. So like a window AC is not split. It’s packaged, everything’s in one package, you stick it through the wall and it cools inside. So split means you mean have an outdoor unit and an indoor unit and the outdoor unit, a lot of people still call the condensing unit. Because when you have an air conditioner that’s what it is. But when you have a heat