Building Science Corporation

Westford, MA, United States

Building Science Corporation

Westford, MA, United States
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Lstiburek J.W.,Building Science Corporation
ASHRAE Journal | Year: 2015

Sometimes the obvious is not so obvious. And the sometimes not so obvious becomes obvious. For example, installing leaky ductwork∗ in a vented attic is a pretty dumb idea (Figure 1). It leads to negative pressures and high air change that, depending on the time of year and climate zone, results in part-load humidity problems, ice damming, excessive energy use, loss of comfort, whatever. If radon was valuable we would mine it this way. Where there is an attached garage, we call it the suicidal option. Everyone pretty much gets it. Copyright 2015 ASHRAE.


Lstiburek J.W.,Building Science Corporation
ASHRAE Journal | Year: 2015

Things have evolved considerably since the Eisenhower and Diefenbaker years. Hutcheon† taught us about airflow that decade but it took more than a half century to get it right. We needed air control. We needed an air control layer - An air barrier. We started off with locating it on the inside and finally ended up with it on the outside.‡ We started by combining it with a vapor barrier on the inside then we finished by combining it with a weather resistive barrier (WRB) and continuous insulation on the outside (Figures 1 through 5). Copyright 2014 ASHRAE.


Lstiburek J.W.,Building Science Corporation
ASHRAE Journal | Year: 2015

Vitruvius had it right 2,000 years ago: "...if a wall is in a state of dampness all over, construct a second thin wall a little way from it...at a distance suited to the circumstances...with vents to the open air...when the wall is brought up to the top, leave air holes there. For if the moisture has no means of getting out by vents at the bottom and at the top, it will not fail to spread all over the new wall.". Copyright 2015 ASHRAE.


Lstiburek J.W.,Building Science Corporation
ASHRAE Journal | Year: 2016

We are adding balconies to everything and people are forgetting that balconies are more than decoration but also have to function. And when we get it wrong it can be catastrophic.† We are going to be dealing with wood balconies due to their popularity and because they tend to get done wrong more often than concrete and steel balconies. Aside from the obvious structural engineering issues dealing with water is the number one issue.


Lstiburek J.W.,Building Science Corporation
ASHRAE Journal | Year: 2011

Joseph Lstiburek, principal of Building science Corporation in Somerville, talks about the building rules and airtightness of the structures. He talks about the blower doors which are considered by some designers as a leakage measuring equipment. But, according to the author, it can only measure equivalent leakage area, not the real leakage area. He suggests that people can install a ventilation system and code-compliant combustion air for less than $500, which is about the cost of a blower door test. Houses without controlled ventilation systems are subject to increased levels of contaminants as airtightness goes up. Houses with standard atmospherically coupled combustion appliances without provision for dedicated combustion air are subject to back drafting and spillage as airtightness goes up. Controlled ventilation and combustion safety are not only good, but necessary.


Lstiburek J.W.,Building Science Corporation
ASHRAE Journal | Year: 2016

It is not easy to separate town houses and row houses from one another (Photo 1). And from garages. And, of course, from the outside. No one really cared until recently. Ah, we had fire walls, but did we really care? Nope. We didn't measure the air leakage of the units themselves. The fire walls did separate the units from one another from "a fire perspective," but the air leakage around them, along them, and through them was pretty much ignored".


Lstiburek J.W.,Building Science Corporation
ASHRAE Journal | Year: 2016

There. I said it. It just does not work. OK, it works sometimes.∗ But it does not work in tight building enclosures and certainly not in new houses, apartments, town houses and row houses. Basically in nothing new that we are building. Because it sucks-literally. I know we were here before ("Unintended Consequences Suck," ASHRAE Journal, June 2013), but we have to come back and deal with it again. Why? As amazing as it seems, things have gotten worse and are going to get worse. But the good news is as they become intolerably bad, we will end up finally dealing with them. Not quite there yet, but almost.


Lstiburek J.W.,Building Science Corporation
ASHRAE Journal | Year: 2016

Huh? Blasphemy. Yeah, well, in some assemblies, a double vapor barrier is actually a pretty good idea. The most famous double vapor barrier of them all is a classic compact flat roof. Check out Figure 1. The roof membrane on the top is clearly a vapor barrier. In fact, it is almost a perfect vapor barrier. And, the membrane on the bottom is also a vapor barrier. The bottom membrane's primary function is that of an air barrier, but its material characteristics are such that historically it has also been a vapor barrier. Copyright 2016 ASHRAE.


Lstiburek J.W.,Building Science Corporation
ASHRAE Journal | Year: 2016

We continue to insist on putting ductwork in attics. It is a dumb idea from an energy perspective - a couple of HERS penalty points at a minimum - and we continue to see condensation on the ductwork in the summers. We have tried almost everything to get the ductwork inside. We have tried dropped ceilings (Photos 1 and 2). We have moved the inside to the roof deck (Photo 3). We have tried burying the ducts (Photo 4). Almost nothing has worked. Well, not really.


News Article | August 26, 2016
Site: cleantechnica.com

What if it was easy to find out how much energy a home uses and how much that energy costs? It could unlock a whole new market that doesn’t exist today worth hundreds of billions. According to an Elevate Energy study, Chicago homes that disclosed energy costs sold almost ⅓ faster (43 vs. 63 days) and had higher deal closing rates (63% vs. 53%). Barry Haaser and Jeremy Roberts at the Green Button Alliance noted studies in Illinois and Washington DC that said simply disclosing energy costs raised average sale prices by $4000, regardless of energy use. Transparency is the likely reason for this – there is less uncertainty and friction in the transaction. Putting a metric on energy use that is easily comparable between homes could begin to value efficient homes more in addition to this effect. The question becomes what metric(s) is best for doing this? Rather than a laundry list, we need to focus on one or two that could fit in a 50×75 pixel box on MLS. If Zillow/Trulia added it to their listings, that could be the essential first step. I propose Energy Use Intensity, or EUI as kBTU/square foot/year. The rest of this article will show my reasoning. Focusing down to one or two metrics forces us to think of them in multiple levels. The metric we should be looking for is top level, similar to combined city and highway mileage for a new car. That helps narrow the field of what vehicles to consider, once we narrow down, then we dig deeper into more metrics like what city and highway mileage are, horsepower, safety features, etc. In the home buying process, this metric will be used at the stage right after prequalifying. For example a buyer qualifies for a $200,000 loan. What that really means is their income allows them to spend $950/mo at 4% for 30 years. Enter an energy metric. The real cost to own this example home includes taxes ($200/mo), insurance ($100/mo), and utilities ($200/mo). So what you’re really looking for is about $1450/month including all costs. This ignores maintenance costs for now. What if one of the homes being compared is Net Zero after solar panels and a Home Performance upgrade? Now utilities are only $35/mo for meter fees. That frees up $165/mo out of the $1450. $165/mo at 4% is $22,000 over 15 years or $34,000 over 30. That means a house with those energy bills vs. a comparable home is likely to be worth $20,000-$35,000 more than its comps. Possibly more because a home like that is likely to have fewer maintenance issues since efficient homes usually have lower air leakage rates and lower air leakage typically leads to fewer moisture problems. That’s for the market to decide. Right now the market can’t see energy costs, so it doesn’t value them. If we knew how much operating costs were for 5 comparable homes, and one home had double the operating cost, that would be an easy way to potentially cross one home off the list. That’s what this metric needs to do. The trouble with cost alone is that it’s very squishy. It’s not a useful metric over long periods. Costs go up and down. The same house may cost $200/mo with lower energy costs, but 10 years ago when costs were higher it could have been $300/mo for the same usage. Different fuels experience different pricing ups and downs. Fuel costs aren’t directly comparable either, an oil heat home generally costs a good deal more to heat than a comparable natural gas heated one. In my opinion, the top level metric needs to be usage based, cost is a secondary metric, although a close second. If those are the benefits, there are a number of things this top level metric needs to do well. EUI (site) has all of these except the raw part. I feel it’s worth the sacrifice for that one item, particularly because with only three numbers behind it – electric usage, heating fuel usage, and square footage, it’s easy to figure out if any funny business was going on. Plus it has a unique benefit: In kBTU/square foot/year the scale for EUI generally falls in a range between zero and one hundred. This is very similar to a HERS score, and like a HERS score, zero is net zero. A 0 EUI means either no energy usage or completely offset energy usage. EUI 100 is a bit piggish, but not awful. Explaining what 6.4 million BTUs per year means to a homeowner sounds like work. Explaining 0-100 sounds very simple. Here is a chart of Energy Smart Home Performance’s projects using EUI using the ResiSpeak tool: The highlighted home with a 24.9 EUI is an all electric Deep Energy Retrofit for Hiram College called the TREE House. Is it possible that home might be worth more than the home at 100? (Ironically, that is my house.) Passive Houses aim at 4.75 kBTU/sf/yr for heating and cooling. 475 Supply is named after it. The Department of Energy has the Building Performance Database which uses EUI and has data on thousands of homes across the US. It’s not something new we have to come up with. In fact, here are my projects overlaid on the Building Performance Database homes in Ohio: EUI only needs fuel usage and square footage. Fuel usage usually comes from utility bills, so those are tough to game. We’re down to gaming square footage. I propose we use county record square footages. County records have these attributes: My argument is for two primary energy metrics: Energy Use Intensity (EUI in kBTU/square foot/year) and total annual energy cost. These are only ‘top level’ metrics. The raw data needs to be available so that deeper analysis can be made when narrowing to a few home choices. These metrics can create total transparency around ownership costs of homes and influence home values, opening up a new market for Home Performance upgrades and lowering risks for lenders. Lower risks mean lower interest rates, which mean more projects make economic sense: a virtuous cycle. This virtuous cycle can lead to numerous societal benefits: jobs that can’t be exported, reduced pollution, reduced health consequences from that pollution, and an easier transition off of fossil fuels because more homes will be capable of going all electric. (We have four pre-1920 all electric homes under our belts now – one is getting solar panels this month.) There are many more benefits that could be argued for as well. All because we started publishing a few numbers. Is this rosy? Of course, but it’s probably not that far off. Chant with me: EUI! EUI! It’s not that hard to make it a reality, if Zillow and Trulia add it, or the National Association of Realtors pushes for it, it could happen very quickly. The Green Button program can be used with monthly data, making data access for easier. This isn’t that hard of a lift. If you have any interest in helping, reach out! This 1900 Cleveland home had a substantial energy retrofit. A 53% air leakage reduction, complete insulation package, and new forced air HVAC system including ductwork and fresh air was installed. It doesn’t look any different than it used to, but it’s much healthier and comfortable than it used to be. The EUI last winter was shockingly low: 10.9. That was unoccupied during a mild winter with a low set point, I look forward to seeing what it is this winter. Shouldn’t this home be worth more because of these upgrades? You can read more about the project and it’s “womb-like comfort” here. Building Science Corporation – Kohta Ueno – Review of building energy use metrics. A great overview of energy metrics. Ironically he argues against EUI, but Ueno’s aim is understanding the deeper implications of energy use, not a top level metric for driving market value. Well worth a read. For more insights on pricing home energy efficiency, here’s an article CleanTechnica‘s Kyle Field published on the topic earlier this year: Buying a house is an exciting part of life, the start of a new chapter, and frankly…freakin’ scary! Typically that’s not because of any spooky creatures but because of the massive mortgage that people usually take on to afford one, the number of things that can go wrong, and unforeseen financial burdens that these ‘money pits’ can become. Many of the financial pitfalls can be identified early on in the buying process as part of a quality home inspection, but there’s one big dirty secret that many homes have that is a bit harder to wrap your head around when buying a new place – energy. I’m not talking about the qi (or ch’i) of the house or anything like that, but literally about the energy used by the house on an annual basis in all forms – electricity, natural gas, propane, heating oil, solar, wind, solar thermal, geothermal, etc Let’s back up a bit. Pretend you’re buying a new car. Do you check the window sticker to see what options it comes with? How about the fuel efficiency? Estimated cost to operate for a year? Me too! …and it’s the same for a house. We want to know which energy options it comes with. Does it use natural gas for heating? Have a high tech heat pump in the basement that is dirt cheap to own and operate? Fuel efficiency similarly translates into energy intensity. You thought I was going to say energy efficiency there, right? The actual metric for putting data behind this is the amount of energy used per square foot of the house. Roll that up over the size of the house and the months of the year and you get the mega-metric – the total cost of energy to operate for a year. Before cars kept track of fuel efficiency, knowing what miles-per-gallon your car got was irrelevant to the market – you don’t care what your car gets and the market doesn’t value it…and it’s the same thing with a home. You can invest $15k in solar panels, $10k in energy efficiency improvements, and $3k in a new heat pump, but you’re not going to see much of that money rolling back into the valuation of the house because people don’t speak that language yet. We need to retrain our brains, and the market, to accurately value not just the cost of the house but the cost to run the house month to month. For example, let’s dig in to the numbers on two houses: Obviously the second house is worth more, and is a better value for the same purchase price. But just how MUCH more does an energy bill that’s $400 lower (every month!) make the house worth? Backing up a bit, how do we even quantify the monthly cost of energy for a house? Putting a price tag on the cost of energy is the first step in getting a handle on the value of residential renewables – such as solar – into the valuation of the house. That allows homeowners to see the month-to-month cost and quickly extrapolate the cost of energy over the life of the house (the long term cost of energy). This could be accomplished by reapplying the concept of the Energy Star label on appliances: Beyond just the base concept of putting a dollar value on, and an increased visibility of, the cost of energy, less efficient homes are actually more risky to banks. Think about it. In the example above, house A carries an energy bill of $450/month vs house B with just a $50/month bill. That’s an extra $400 of monthly debt on house A that will never go away for the homeowner. That effectively takes the monthly payment for the house from $1000 to $1450 whereas House B is only going to cost $1050/month – a huge difference. One of my favorite sayings that I’ve heard about solar is that it takes a monthly liability (the monthly bill) and turns it into an asset (increased value of the house). Homes with higher energy bills are riskier investments for banks, as the monthly energy cost is not taken into account when the home is financed. It’s essentially a highly variable chunk of debt (particularly in this era of increasing efficiency and solar) that the bank not only doesn’t know about, but doesn’t seem to care about. In markets where the energy bill is a large percentage of the mortgage, this can play a large factor in whether a homeowner can actually afford the full cost of the home or not. Further, the variations in energy price can, and likely often do today, single-handedly sink the homeowner’s monthly budget and kick the loan into default. Finally, these energy costs can be rolled up over the life of the loan as part of the purchasing process. House B might only cost $18k in energy costs over 30 years whereas house A would tip the scales at $162k!! Granted, not many people are interested in stepping back and looking at the total cost of energy over 30 years, but lifetime costs often paint a picture compelling enough to trigger small changes. If we looked at energy costs this way more often, solar and energy efficiency would be much more likely to have increased value when the house hits the market. Markets value what is measured. We need to measure energy use and turn consumption into an easy to understand comparable metric – like MPG is for fuel efficiency. Doing that will trigger banks and financial institutions to dig a bit deeper into the value of energy efficiency and residential power generation as a part of the lending process and overall risk assessment. If Energy Use Intensity is being looked at by financial institutions, services like Zillow will start reporting EUI, which completes the cycle back to the consumers. Homeowners would have more incentive to invest in technologies that are better over the long run and often for the planet, such as making that $5k investment in more insulation, spending $300 on LED light bulbs, or $15k on solar. Homeowners can have the confidence that they are making an investment in the house and in a reduction in monthly operating costs over the life of the home, or at least of the product being installed. For LEDs, that’s just 22.6 years…what a ripoff 🙂   Drive an electric car? Complete one of our short surveys for our next electric car report.   Keep up to date with all the hottest cleantech news by subscribing to our (free) cleantech newsletter, or keep an eye on sector-specific news by getting our (also free) solar energy newsletter, electric vehicle newsletter, or wind energy newsletter.  

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