Party Walls

Most of us are familiar with the feeling of a humid apartment after taking a hot shower. Some of us kick on an exhaust fan, perhaps un-fog the bathroom mirror, or even open a window to get the moisture out. Domestic moisture generation—moisture from human activity—is a major factor driving the humidity levels in our residential buildings, especially in super air-tight, Passive House construction. Before diving into just how much of an impact domestic moisture has in our buildings, let’s first look at average daily moisture generation rates of a typical family of three[1]:

• breathing and transpiration—6 to 9 pounds of water vapor/day;
• 10-minute shower in the morning for each individual—3.6 pounds of water vapor;
• cooking fried eggs and bacon for breakfast—0.5 pounds of water vapor;
• cooking steamed vegetables with pasta for dinner—0.5 to 1.0 pounds of water vapor; and
• one small dog and a few plants around the house—0.5 pounds of water vapor/day

This brings the daily total to 11.1 to 14.6 pounds of moisture generation per day, or about 1.5 gallons of liquid water.

Where does all of this moisture go? In a typical code-level apartment building with moderate to high-levels of air leakage, water vapor has two year-round exit pathways: exfiltration through the façade and dedicated kitchen or bathroom mechanical exhaust. Additionally, in the summer, moisture is removed via condensate from the cooling system.

Let’s now put this in the context of a highly energy-efficient apartment with very low levels of air leakage (about 5 to 10 times less than the code-compliant unit), and balanced ventilation with energy recovery. The first means of moisture removal, façade exfiltration, is virtually non-existent given the building’s superior air-tight design. Next is mechanical exhaust ventilation in the kitchens and bathrooms. Because the unit has balanced ventilation and energy recovery, the exhaust air stream in a Passive House project typically passes through the energy recovery core. Depending on the core selection, a large percentage of the interior moisture may be retained in the apartment air despite the constant mechanical air exchange.

There are two basic types of cores:

• Heat recovery ventilator (HRV) in which a certain percentage of sensible heat is recovered (transferred from the exhaust air stream to the supply air stream) while no moisture is recovered.
• Energy recovery ventilator (ERV) in which a certain percentage of sensible heat and a certain percentage of moisture in the air is recovered.

To fully understand this issue, Figure 1 breaks break down the moisture-related pros and cons of ERVs and HRVs in the context of a high-density, Passive House building.

	ERV	HRV
Pros	Summer – prevents high exterior air moisture load from being supplied to interior air; cooling loads are minimized	Winter – flushes high internal moisture load out of building; humidity levels reduced
Cons	Winter – if internal moisture generation is high, interior moisture load is not flushed out of apartment; humidity levels increase	Summer – allows exterior air moisture load to be supplied to interior air: cooling loads increase

Figure 1. Moisture related pros and cons with ERVs and HRVs in high efficiency, airtight construction

 

Traditionally, the key factor in deciding between an ERV or HRV for a high-efficiency building has been the project’s climate. However, as internal moisture loads begin to exceed exterior moisture loads in high-density projects, the decision between ERV or HRV must be looked at more closely for each project regardless of climate.

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Everyone pretty much gets that continuous (or very frequent) ventilation is necessary in high-performance homes. And – at least in theory – most people get why balanced, heat recovery ventilation is better (than unbalanced and/or without heat recovery). But the devil’s in the details.

A couple years ago we started an R&D project with funding from DOE’s Building America program, and one of the first steps was interviewing several developers about ventilation (single- and multi-family residential, mostly on the East Coast). For none of these developers were HRVs or ERVs standard.[i] They all had some experience with ERVs, however, and when asked about these experiences the word “nightmare” came up shockingly often.

The ERVs on the market now can certainly work well in the right application, but we see problems more often than not. One of the biggest challenges is trying to add ERVs on to central heating/cooling systems in homes. Most ERVs aren’t really designed for this, and here’s what we see:

• Ducts connected to the wrong places! Outlet and inlet ducts get reversed, or the supply air from the AHU getting exhausted (sad how often this happens).
• ERVs are attached to supply and/or return trunks of the AHU. Unless the AHU fan is running constantly (or whenever the ERV is turned on), outdoor air comes into the AHU and is sucked right back out the ERV exhaust.
• If the AHU fan is turned on, the relatively small fans in the ERV can’t successfully compete with the big AHU fan. People don’t get the ventilation flow rates they want and/or the flows are very unbalanced.
• AHU fans can use A LOT of electricity. Hundreds of Watts is common – I’ve measured over 1 kW (though this is changing – more below).

Even if installers follow manufacturer instructions for attaching ERVs to AHUs, they could still end up with low flows, unbalanced flows, or high electricity consumption. Through this DOE R&D effort, we’re trying to do better.
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Quick pulse survey: in the last three months, since we published our Part I blog on tips for healthier indoor environments, how many of you have either incorporated some of our healthy recommendations into your home, or informed your clients on the most effective ways to address health risks in buildings (hint: if you need a refresher, please visit Part I)?

As previously discussed, there is overwhelming evidence for the business case for healthier buildings, from greater employee productivity and reduced sick days in the workplace to reduced asthma incidents and ER visits for children living in green housing. Leading organizations know that improved wellbeing helps employees to be healthier and lowers healthcare costs. It also helps employees to be more productive, creative and innovative, and less likely to leave for a competitor. The same concept can be applied to tenants in rental buildings and condos.

Before we dive into health tips #6-10, here are some fun (and not so fun) facts to keep in mind while we spend winter days INSIDE our workplaces, schools and homes:

• In the winter, school-aged children ages 11-17 will spend 60 minutes a day outdoors, compared to 175 minutes in the summer. (Source: Schools for Health by the Harvard TH Chan School of Public Health.)
• In a study of 73 elementary schools in Florida, students in schools cooling with the noisiest types of HVAC systems were found to underperform on achievement tests compared with students taking tests in schools with quieter systems.
• According to a recent survey released by the U.S. Green Building Council (USGBC), employees who work in LEED certified green buildings are happier, healthier and more productive than employees in conventional and non-LEED buildings:
  • More than 90 percent of respondents in LEED certified green buildings say they are satisfied on the job and 79 percent say they would choose a job in a LEED certified building over a non-LEED building.
  • More than 80 percent of respondents say that being productive on the job and having access to clean, high-quality indoor air contributes to their overall workplace happiness.
  • 85 percent of employees in LEED certified buildings also say their access to quality outdoor views and natural sunlight boosts their overall productivity and happiness, and 80 percent say the enhanced air quality improves their physical health and comfort.

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How many of you out there would say you are happy at your place of work? Are you having a hard time concentrating? Now, take a pulse on your surroundings. Are the lights too bright? Are you too cold? Too hot? Do you hear constant humming from the HVAC equipment in the background? How much sleep are you getting at night? How many plants are in your view? Do you even have a view?

I’m sure many of you have heard the statistics that we spend nearly 90% of our days indoors. BUT, did you know that:

• 75% of deaths are caused by chronic disease, up from 13% in 1800;
• Today’s children are the first generation expected to have a shorter life expectancy than their parents;
• 85% of the 82,000 chemicals in use are lacking in available health data.

When we hear the term “high performance building,” many of us think about energy efficiency first. But, what factors contribute to human health in buildings? How do we design for and maintain efficient building performance without compromising occupant health and well-being? What benefits are associated with healthy homes and work spaces? These are the questions we should be asking ourselves.

Lots of research has been done. Pulling from the LEED, EGC, and WELL concepts, and supported by case studies (specifically Harvard’s School of Public Health’s 9 Foundations and Stok’s report on how workspaces that promote health and wellness), here are SWA’s Top 5 (of 10) tips to effectively address Indoor Air Quality (IAQ) in buildings:

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A team of SWA consultants recently had the opportunity to tour the newly constructed Delos Office Headquarters, located in the Meatpacking District of New York City. The office, which occupies the fourth and fifth floors of a ten-story building adjacent to the High Line, has obtained WELL Platinum certification through the International WELL Building Institute (IWBI), Petal Certification through the Living Building Challenge, and is currently pursuing LEED v4 Platinum certification through the US Green Building Council (USGBC). From the inception of the tour, it was clear that the space had exceeded the expectations of these certifications, and more.

Overview

Stepping off the elevator, occupants walk over a large metal grate designed to remove debris from shoes, preventing dirt and other particles from contaminating the floor. Then, upon entering the office, visitors are immediately greeted with an abundance of natural light and sense of biophilia. The office is enclosed by large glass curtain walls and filled with an array of plant life. Next to the entrance, a large monitor displays office conditions, such as temperature, humidity, carbon dioxide, and other levels affecting tenant comfort.

The main office area is largely free address, which means employees can freely move to where they feel most comfortable. Each desk is adjustable and includes a monitor, a temperature adjustable task light, and many other utilities that foster productivity. There are greenwalls placed throughout the office (22 to be exact), which are used to purify the air. Clean air is also distributed through floor diffusers and dirty air is removed through the ceiling. Additionally, it is noticeably quiet in the office; the mechanical systems are well insulated and there is a low level white noise sound masking system that lessens harsh noises.  (more…)

National Public Health Week is this week and Today’s theme is “Environmental Health”, which includes protecting and maintaining a healthy indoor environment.

While National Radon Action Month was in January, we wanted to share how this specific indoor air pollutant can affect your health and what compelled a group of us here at SWA to get our homes tested (and remediated).

What is radon and why does it matter?

Radon gas is a naturally occurring byproduct of the radioactive decay of uranium found in some rock and soil. You can’t see, smell or taste radon, but it may be found in drinking water and indoor air. This carcinogenic gas is currently the second leading cause of lung cancer after smoking, according to the National Cancer Institute.

Although radon in drinking water is a concern, radon in soil under homes is the biggest source of radon, and presents the greatest risk to occupants. This pressure-driven mechanism occurs when radon escaping the soil encounters a negative pressure in the home relative to the soil. This pressure differential is caused by exhaust fans in kitchens, bathrooms and appliances, as well as rising warm air created by furnaces, ovens and stoves.

Radon levels can vary dramatically within a region, county, or city. However, the EPA recommends that all homes be tested, regardless of geographic location. To see what the average levels are in your area, check the EPA Radon Zones map.

What radon levels are accepted? Ideal?

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The International Energy Conservation Code (IECC) has a number of requirements involving energy recovery on ventilation systems. Requirements vary based on climate zone, building type and size, equipment capacity, and equipment operating hours. As a result, many new construction projects must now incorporate energy recovery considerations into their design.

An energy recovery unit (ERU) equipped with a heat wheel can be a great way to satisfy these energy recovery requirements. The ERU can be a roof-mounted air handling unit, or can be an air handling unit located inside a mechanical room with outdoor air and exhaust streams ducted in. The heat wheel is positioned so that half of the wheel sits in the exhaust air duct and the other half sits in the outdoor air intake duct. During cold weather, the wheel spins, transferring heat from the exhaust stream to the outdoor air intake stream. During hot weather, the wheel transfers heat from the outdoor air intake stream to the exhaust stream. In both cases the heat exchange enables the building to take advantage of the more comfortable conditions of the exhaust air, while still allowing fresh air to enter the building. During extreme weather conditions, heat wheels can save energy on space conditioning while still allowing for healthy indoor air quality.
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Healthy Building Materials as Contributors to Overall Human Health

What do you think of when you hear the term “healthy living?” A balanced diet? Physical activity? What about healthy building materials? The concept of healthy living can — and should — be extended to include anything that can affect people’s health either directly or indirectly. With this in mind, the impacts of building materials on occupants’ health is a growing concern of building industry professionals because exposure to unhealthy chemicals used in building materials can trigger serious health hazards.

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Post written by Chelsea Wales, SWA Intern in Washington, DC

“Human centered design is a creative approach to design solutions that are tailored to individual users. Oftentimes human centered design is about building a deep empathy with the people you’re designing for; which is critical when we design for people with disabilities.” That’s how industry experts Katie Osborn, Hansel Bauman, and A.J. Paron-Wildes define this innovative design approach. On August 2, 2016 the American Institute for Architects Committee on Accessible Design located in Washington, DC hosted its first-ever panel event entitled, “Trending Strategies for Human Centered Design”. The District Architecture Center was bustling with people of all ages, backgrounds, and abilities as they filled the glass-walled lecture room to hear the industry thought leaders discuss the importance of human centered design.

Moderated by SWA’s own Senior Accessibility Consultant and Accessibility Committee co-chair, Victoria Lanteigne, the panel format allowed for each human centered design professional to share their stories and expertise in their respective fields. Following the presentations, Victoria lead the panelists in a group discussion which ended with a Q&A session during which audience members asked their own questions related to human centered design. (more…)

In SWA’s second contribution to Green Energy Times, we examine the certification programs, operational strategies, and occupant behavior trends that contribute to enhanced indoor air quality (IAQ). The full article is featured below, or on page 29 of the April-June edition of Green Energy Times.

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