Denver Vibe Interview: What Makes a Passive House?
In December of last year, Principals Steve and Morgan were interviewed by Denver Vibe, a blog by realty partners Antionette Wharton and Nicole Rufener of Mile Hi Modern. They wanted to share an in-depth explanation of the Passive House approach and how it contributed to the success of Denver’s first Passive House certified multi-family home, recently completed in Englewood, Colorado. Read more about the project here.
Nicole: My name is Nicole Rufener I'm a realtor with Mile High Modern and the founder of Denver Vibe. This is my business partner.
Antoinette: I'm Antoinette Wharton with Mile High Modern and Denver Vibe.
Steve: Steve Scribner with Shape Architecture Studio in Denver, we specialize in high performance Passive House homes.
Morgan: Morgan Law, Shape Architecture
Antoinette: Thank you guys for being with us today in this beautiful home! We are on 3591 South Ogden and want to learn more about a passive home.
Nicole: So our audience probably has a wide range of knowledge of what passive homes are, can you just first describe what that is?
Morgan: It's an energy and comfort standard that promotes a 90 reduction in energy use in the building and also has extreme elements of comfort and acoustic separation that are natural and mechanical ventilation. What that means is that you get constant filtered fresh air into the house, much better thermal comfort than in most other homes and a reduction in your overall energy so over the year.
Steve: And add to that it's actually super healthy. So for instance, right here we're sitting next to 285, an eight lane highway on a hill. It's a lot of engine braking and a lot of acceleration, a lot of exhaust and because there's continuous fresh air, ventilated pressure in the home all the time, the air we're breathing is extremely healthy. Compared to a conventional home, where air would be filtered through the cracks in the walls that has sort of seeping through, so you get all that exhaust plus maybe some insulation bits.
Antoinette: So even houses a couple doors down are breathing really, you know, toxic air whereas this one's right next to it and its completely clean air. That's fascinating.
Steve: And Denver actually does not have great air quality overall, it sort of ranks low in cities in the US.
Antoinette: And I know with passive homes, the health component is a big part of it. And a big part of that is just the quality of the air. What other elements are a part of the design process that you're thinking of that contribute to the health of a home?
Steve: So the interesting thing about Passive House compared to for instance LEED or other performance guidelines is that it's actually almost like a building code and you actually have to do an energy model as you do the design. So you sort of build a house virtually and then calculate how much energy is being used and lost, and not only that but what the comfort is going to be inside. So windows have to meet a certain comfort standard. So if it's zero degrees out and say 70 in, and you're right next to a window, that window is going to be above 60 degrees so you're not going to feel the kind of cold coming off it and that's part of the standard. And then what's great about the energy modeling process is that after you complete the design and it's built, passive houses always perform completely aligned with the energy model that was put into it. So this house is using as much energy as it was designed to use, whereas a lot of the other standards are a little bit more guesswork and they don't necessarily always perform the same way as they were designed. Because we're looking at one thing called Thermal Bridges, which is secret paths with passageways for heat to get to the outside through say steel beams or other kind of structural elements, you know cantilever, balconies etc., can let a lot of heat out and so that means the performance of those buildings isn't the same as what the model performance is whereas with Passive House you know it is. And then people, when they're in in passive houses, they're like WOW it feels different between the the quietness from exterior noise, the natural light as you can see, it's very light bright here and there's no lights on. And that was really part of careful design to make sure again, here we’re on 285, we didn't want to have South-facing windows but we need the heat that comes with the light from the South, so we have the central three-story staircase window well that brings light very deep into the house while keeping us really comfortable. There's no glare, and there's no heat loss. There's the right amount of heat gain in winter/ summer.
Morgan: I think there's a misconception too on passive moments from the 70s or 80s that just have these big walls of glass, and then the houses would heat up quickly and dramatically and then cool off a lot because it has a wall of glass on it; whereas you can see compared to this house there's relatively little glass on the South and we're not relying on that as much shading is also an important part of that to keep the house comfortable and stable throughout the day and throughout the year. So I think that's that's an important thing and then typically when we design these houses, we're not relying on some big mechanical system that can ramp up and ramp down, it's a third the mechanical system, it's a third of the sun, and it's the third the people; and the internal gains and equipment inside those. So those three things are what power the house and you can tell right now the mechanical system is not even hot right, because we have basically two out of the three going right now and that's enough to condition the space.
The other fantastic thing about it too is that it's able to weather temporary outages much better just due to the thermal mass, the increased insulation, so when we get these temporary power outages this home can basically maintain the temperature for as opposed to a couple hours it's more like a couple days.
Nicole: Wow.
Morgan: And you know, that's especially true that you have a party in here, like start increasing the occupant load and then it'll stay warmer even longer.
Antoinette: So we'll all flock here for power outages. Have a party!
Morgan: Exactly.
Steve: And it's not hypothetical. We have another Passive House that was completed, and the owners are living in it now, a couple years ago. And they've had a temporary issue with their mechanical system, and it's hard to get mechanical contractors so it's been a couple of months and they literally have had no heat and their temperature has been staying between 67 and 71 degrees -
Nicole and Antoinette: Wow.
Steve: - with zero heating and cooling. And that's because we designed it with the right amount of south facing glass; and it's just an efficient, fairly simple design. So it really works. And that's, I mean thinking long term about you know, the potential climate disruption or change, having something that you don't even have to power to be comfortable in, we see it as kind of a mandate for all of our work.
Nicole: I know you guys have talked a lot about how it's socially responsible too - given what we're looking at with the climate. But I love what you're talking about with just that exchange of when you approach a site you're having to look at how will this house work, and just connect with the neighbors and work with the neighborhood and community. But also I love what you're talking about just with the people in the homes and also have that exchange within the home itself. So it's just a much bigger way of thinking of design within a community versus just one house and what that design is as well.
Antoinette: What do you guys think is your favorite feature of the home?
Morgan: I mean the kind of open stairwell that connects all the spaces and just kind of floods the whole house with light - and you know creates these like really nice views out but it still feels completely cozy and protected over here kind of close to the road. I think, you know these kind of tight urban lots where the privacy can be an issue, it's a good way to get a nice quality of light in this space without a compromising privacy issues.
Steve: And then another sort of trick we did is on this unit - we have a skylight that actually brings light in through the third floor party deck into the second floor master bath and it's sort of, you can see it when you walk in. It makes this really even light, there's no glare but just a sort of like magic light coming in; that was one of the design features we were really excited about trying and we were really excited that the developer Peter agreed to do it and tried it and it's actually very successful.
Antoinette: It's beautiful in there. It’s very serene.
Steve: And I can't help but wanting to add the party deck - it really does frame the mountains really, really wonderfully and something that we couldn't really tell before the building was built to see how that design can work out and it worked out really well - and also because the roof to that deck is open, it brings light into the party room, on the third floor. It could be an office, a loud game room, kids playroom, family room. But always that's going to have that great natural light and the views of the mountains as well as the access to that.
Antoinette: And we were just talking about the roof - how it's set up and how other homes work when we have snow melts. So do you want to elaborate on just the uniqueness of the roof lines?
Steve: Sure! Yeah, so there's a pair of gables next to each other, so like - pitched roofs - and between them, that makes it a valley, which is something that's a really good idea to avoid a typical construction - because at those locations where there might be a valley, typically heat will come out of the house through the roof and it will melt the snow, and then if it's cold out that snow will refreeze and form ice and ice dams, which can be a problem for a long term the maintenance, durability. But because it's a passive home, this insulation thickness is so great that the roof surface is always cold. So in winter when it's cold out, the snow is not going to melt. And it's only going to melt on warmer days when the sun is melting it and it can, you know, drain into the gutter. So we should not be seeing any maintenance issues with that but it's just another thing with the Passive House, making sure we're also being careful about not having steel or something that would sneak the cold, the warm air, through the envelope.
Nicole: So we touched on this earlier, just common misconceptions about passive homes, um, so can you explain because I think some people get confused. We've heard some clients talk about not knowing the difference between passive solar and solar. So can you describe that a little bit more in depth and how that plays out here?
Morgan: Well again yeah, it's a different approach than the older approach to the process of solar homes, it’s increased insulation. A lot of people actually get bogged down by that or confused by that and there's really not that much insulation in this house right, I mean a big part of it is the form factor. The geometry is relatively simple and where you kind of lose energy, its too many corners or jogs, or you know, see these houses that have all these pump downs and things and that's just it's really tough from a energy standpoint when dealing with that sort of geometry. So yeah, there's basically a couple inches of insulation on the outside of these walls but it's pretty typical, it's you know, a two by six wall and very standard stuff. So um yeah, I guess that would be the first element of it.
Steve: And I think the fact that it's a duplex helps a lot, because energy is sneaking through this well a little bit, but we have really high performance windows. So there's three panes of glass, whereas a typical new window - double pane, and classic windows are single pane and then even more importantly that where that panes meet the wall, is actually where the these windows, the science and the technology comes into the into the quality of these windows. So no air is leaking through, and then no heat is sneaking through, and that's really important. But then back to the duplex, heat is just leaving this way, this way, and a little bit through the roof - as we talked about not very much - but no heat is getting lost that direction and that's a large amount of surface area, so that right there helps a lot. So it's another social argument, increasing density, also increasing efficiency.
Antoinette: Mmhm yeah.
Morgan: I think another big difference is to get certified, there's an air tightness requirement which means the house is like a super tight envelope - right - and so as opposed to something like LEED or something where you're filling out these checklists, that air tightness is the responsibility of the builder. So historically that's why we've seen a lot of builders interested in the standard, because they have to actually up their game and get this super small requirement of air infiltration into the house, so that obviously is another element of a passive home versus a passive solar home in that, all of a sudden we get this really tight envelope box, right, there's no air coming in or out. So that's why we introduced the mechanical ventilation that filters the fresh air that's constantly supplying air into the living spaces and extracting it from the bathrooms and the kitchen. So there's this kind of constant flow that's creating this fresh air into the space, and helping to deal with that tight envelope.
Another thing people get confused about is operable windows; we’ve heard, “Oh we'd like a passive house, but we like to open our windows.” you know, which is yeah, it's just another kind of misunderstanding about the Standard, you'll see throughout this house most of the windows are operable.
Steve: They're required to be, by Passive House Institute.
Morgan: Right, yeah exactly.
Steve: And it's great you know, it might overheat a little bit in the afternoon, the window it's um, it's part of people's emotional comfort.
Nicole: It's just too bad they build the road there, you know, right when you're building this beautiful home.
Steve: But you know what? It's great.
Antoinette: Because you have the fresh air!
Nicole: I swear it only takes like five minutes to be in this home to feel like my respiratory system is normal instead of the like you were saying Denver air quality is not great and so I love spending time in here. It's just you can feel healthier while you sit here. So it'd be a great place to live.
Morgan: Another weird thing people experience in Passive Houses is to maintain their temperature throughout the day and night. So most of us are used to turning down our thermostat and then trying to save energy and we just throw our extra blankets on, it's cold and our house kind of goes up and down. And when you sleep in these houses it's just so weird, you wake up it's like still 70 degrees and the heat's not on…
Nicole: So lovely, that contributes to comfort in the home versus sacrificing comfort to sleep better.
Antionette: Well we are in the middle of winter, but how does the AC cooling, if we're in the middle of summer and we have the sun coming in, can you speak a little more to that efficiency and how that works?
Steve: Absolutely. Well the first thing is that in the summer when it's hot sun is higher in the sky, so you get a lot less energy coming in through the windows and that's part of what we do with passive home designers is really think about where there's going to be shade on surfaces and when - and really specifically through the seasons.
Morgan: And so that deciduous tree out there was actually put in to complement the building depending on the season.
Antionette: I love that tree especially when we were shooting the photos right at like the fall, it was so orange and beautiful and yellow it was like this is… a good job on the tree. It’s beautiful.
Steve: Deciduous trees are basically the best shading devices that could ever have been designed. Amazingly because it allows a lot of heat in the winter and not in the summer.
The other thing is that the heating system - it’s all-electric house, and there's what's called mini split heat pumps in the home as heating and cooling - and they do both heating and cooling super efficiently. Basically if you put in one unit of electric electricity energy you get 3-4 units of heating and cooling out - so that's more than 3x as efficient as the most efficient boiler for a conventional or even many more times more efficient than a gas furnace. And then they're also very quiet, they have variable speed and this house has three of those units which are the smallest that are available on the market, and that's still more energy than is required for this whole house by a factor more than two - because you can't even buy in America a unit small enough for Passive House. But they're very efficient even at if they're not operating at full capacity. Again, with conventional systems, you kind of have to figure like cycle - they're either on or off - but they do great for cooling.
Morgan: They also work great if you were to, both of these homes could have solar panels installed relatively easily, with like the few panels basically you could be Net-Zero.
Antoinette: I thought you had mentioned that the amount of solar panels required also is significantly less than on a standard home - or even a LEED home right?
Steve: Yeah. And your question was the difference between passive solar and solar - so there's the conventional, the classic understanding of like a solar home; but then active solar - photovoltaic panels - is usually people's first go-to sustainability measure. But it's actually, they take a fair amount of energy to produce, so true sustainability comes from not needing energy, and then the backup to that is to put on solar panels.
So we often do Net-Zero homes and it starts with a Passive House approach, and then adding solar panels as needed, which is is a lot fewer. Especially in the climate - we have a really like great climate here for this because the homes are so tight, it gets really cold at night and really warm by day and those kind of average out to a great temperature. And so because it keeps all that that heat in, it works really well with that. If it were to stay negative 20 for two weeks and it was great all day…
Antoinette: Different conversation, yeah.
Steve: The question of how much one saves from having a Passive Home is actually impossible to answer - and that's partly because right now, gas prices are really cheap. So comparing all electric to gas, gas is so favorable per unit of energy - but that's not long-term thinking. And this home for instance, does not have solar panels, but once you have solar panels - the South unit could be Net-Zero - the North unit presumably would not be able to meet that. But Net-Zero meaning you spend zero dollars on electricity except for cooking basically.
Morgan: I think another way to think about it is - I've talked to some friends who work in finance about this because we get that question all the time - and it's like really hard right, it really depends on the size of the house, the location, so many different things. But the way that I've heard it described to me from someone smarter than me is, you are kind of taking that money that you would be spending on your utilities every month and you're moving that over to your mortgage payment so there's an increase in cost. But when you go to sell that house, or at the end of the mortgage, you have a much more resilient home that will last a lot longer than a typical house. So I think price-wise it's kind of a wash. I mean you're either giving it to utilities or you're investing in your mortgage. And you know for most of us the latter would make sense. And then I think that also doesn't really talk to the health benefits that you're getting throughout that investment.
So is it worthwhile if you're going to own the house for a year? No. Is it worth it if you're going to own those for five or ten years? Definitely.
Nicole: I think even a year to be in this fresh air every day would be fabulous.
But then there's the intangibles - like the way we're going, and what people value. We know in real estate that people are going to value a healthier home, a home that you don't have to replace the mechanicals or just beautiful design that sustains the test of time. And so I think there's a huge value there and people will pay for that because people understand it. And more and more, I think people are going to see more passive homes here and understand that and see that value. And so it's kind of intangible now, but we're going that direction more and more.
Steve: People I think see Passive House as sort of niche, sort of nerdy approach to comfort, you know, houses that are for those people that want to sacrifice themselves for the environment - but it's the opposite - it's a way to make a more comfortable house, that has more pleasant daylight, better acoustics, and the health benefits are not quantifiable, but really real. And really profound. Major, major impacts on society at a societal level, and then the durability, you know this house is a 200 + year house, and nothing built between 1950 and 1990 can say that. There is mold in every wall, and in all of the new condos that have gone up at least 20 years ago because of the building practices. And so having all of those things combined are why we do this. We do care about the environment, maybe that's why we got into this, you know, got trained. But it's not actually the reason that people should do it. It's a benefit that's on top. And then especially again thinking long term - in 30 years are gas prices going to be what they are right now? In 30 years are the prices of solar panels going to be where they are right now? One's going up the other is going down. So I think it's like thinking about your investment in this and then adding to that state and national and local incentives for sustainability measures which are getting to be pretty substantial.
Nicole: Absolutely. And in our understanding, the city of Denver really wants everyone to go electric in the long term, so better to be ahead of that curve than at the end of it and looking for stuff to replace and just reconfiguring a whole system in a house.
Morgan: I think in 2015 when we started, Passive House was this really weird, niche thing that was going on and like at this point, Excel Energy is offering a $45,000 rebate for homes for the Marshal Fire victims if they go to the Passive House standard. So it's it's being adopted on a much wider scale that is very exciting.
Steve: And they're doing that for an economic reason. They are not doing that because they want to save the world. They wanted to do it because they're concerned about how they build infrastructure, so they want to reduce people's energy consumption and it has ripple effects that scale really dramatically.
Antoinette: I think what you guys have done here is create this really unique, beautiful… I mean it's beyond beautiful. There's so many up-level finishes and the triple pane windows, and all the health benefits, but I guess what else would you want to say about it being right next to 285?
Steve: Well first of all shout out to Peter Stewart for doing an amazing job with all this - absolutely unbelievable contractor. And his vision right from the beginning, it was completely aligned with everything we've been talking about. But I think he saw the potential in this lot that no one else would have seen, and he also thought it was like an amazing design challenge. Because only with our passive house building science experience, could we take something that is just an obnoxiously loud location - and stinky - and make it into something as comfortable and quiet and peaceful. And it really was through these sort of like architectural strategies of, we need a lot of South light for our passive solar, but we're going to design that in a way that's not where the upper windows are and where it can bring light all throughout the house. And we also need the stairs - so we were able to do it without really sacrificing architecture, and really making the architectural design even more exciting.
Nicole: And what an amazing contribution to the community. Because there's new builds up and down this block that haven't thought through those elements, and you would hear a sounds more, or you would not have the same quality of air. And instead of someone just doing something here that didn't take those things into account, you're contributing to the neighborhood with beautiful architecture and a healthy home.
Antoinette: And all those elements would be ideal for resale. There are things people don't know until we talk about them, so that's why we're talking about them.
Steve: It sounds like we're talking loudly but we're not - because, we’d be shouting at each other in another house.
Morgan: Yeah it's a relatively small lot too, so I think even that connection to the outdoors like we have here, and how we have on all the levels and the stairs, it really helps lessen the need to feel like you need to be outside. Which is obviously louder, so I think that creating that connection in a lot of the gathering spaces is pretty cool.
Antoinette: Yes, yeah absolutely nailed that goal, it's beautiful. And everywhere that you would gather in the home, there’s so much light, so comfortable, it feels really nice. I mean, the rooftop deck is probably my favorite thing about it. But there's so many things I love about it though, I do love the South facing window and the stairs, and again how Peter did such an incredible job with that finish level, but we also love how the A-frame frames the mountain view, perfectly West facing. And you kind of sit up a little higher than the other homes, they kind of go down the hill a little bit more so you have such a great view.
“People I think see Passive House as a sort of niche, sort of nerdy approach to comfort; as houses that are for people that want to sacrifice themselves for the environment. But it’s the opposite - it’s a way to make more comfortable houses that have more pleasant daylight, better acoustics. And the health benefits are not quantifiable, but very real.
”
Nicole: Just for our viewers our listeners if they're interested in this and they either wanted to build their own or find that right house - Specifically if they want to build their own, like where should they start?
Steve: Talk to Peter Stewart haha.
Antoinette: I'm gonna buy this house actually, haha yeah.
Nicole: But I feel like you have to probably be thoughtful in the lot and the site and that will contribute to the look of the home. And what I love too is that you're not going to have cookie cutter homes, you're going to have unique homes that make a more interesting neighborhood when there's eclectic homes, eclectic design. And my understanding is you have to be very thoughtful about the home, how the house would sit and that contributes to what it's going to look like. So yeah, you need to start by talking to you guys, talking to Peter, but any other thoughts of how to get started?
Steve: Well I would say just to thank you for the compliments and that's why we're here, we love creating the best solution for any given site. And the home I referenced earlier, that has only passive heating right now, is much more sort of the not contemporary design. It fits right into this more traditional neighborhood. So there's no particular design style and I think that's another misconception people have…”Oh I don't want it to look like that”.
But I think the other thing to say is there’s a lot of resources. Emu Systems was the Passive House consultant on this project and they are an amazing local resource. They're sort of the national leader in training builders, but they also do consulting. And the other thing that's really amazing about what they do is they do a lot of sort of work to change laws. They've done white papers, they've worked with ASHRAE which is sort of on the technical side, to try to educate people and I think that's part of the reasons we're seeing these changes. They worked with Excel to educate them which has led to this rebate. So people can reach out to them, they're very approachable, if they're interested in more about Passive House. Obviously reach out to us or reach out to Peter, but that's just another resource,
Morgan: And they have homeowners taking their course all the time and so they're basically unleashing this army of certified professionals and architects, builders, homeowners, engineers.
Steve: And I will say I'm LEED certified, LEED AP, I’ve dabbled in WELD Standard, I'm interested in the living/building challenge, but Passive House sticks. Once you do the buildings, because it's building science - it's not a checklist. So once you learn it, even homeowners taking this course, that really do it -understand it - no one ever goes back. Because once you realize it's really simple stuff - it actually is - there's science to it, and there's math you have to do that's not easy math, but it's not complicated. There's only like five kind of basic things you have to hit. And so once you realize that everyone should do this, we do non-certified projects for different reasons, but we really never let go of the underlying building science and high performance approach. Because why should we? It doesn't make any sense. It has so much value.
Morgan: Yeah I think it's a good point. Like as opposed to LEED or something where you're following this checklist and there's a very prescriptive way to reach the certification, with Passive House, you know there's a couple metrics you have to hit, but how you get there is completely up to you. And so I think especially from a designer and builder perspective, that really opens up some different opportunities on how to get there whether it's better windows or better mechanical systems, you know you can really kind of do those trade-offs to figure out the most efficient affordable way to get there if certification is what you’re going for.
The interview continues in the video above.