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Tag: Technically Speaking

Electrifying Central Ventilation Systems in Multifamily Buildings

A common strategy to provide ventilation in multifamily buildings is to design a central roof-top air handler that distributes outdoor air to each unit. The energy cost for this system, which commonly uses natural gas for heating for either a gas furnace unit or hot water from a central boiler is paid for by the building owner. However, there is another option – VRF[1]. With the unprecedented rise of VRF technology in the last decade combined with regulations such as New York City’s Local Law 97 of 2019[2] (carbon emission penalty), the industry is taking a giant leap towards building electrification. There are always questions and concerns raised against building electrification ranging from initial cost to operating cost to reliability of the VRF technology. From the owner’s perspective, the biggest question is usually surrounding the operating cost of an electric system compared to a natural gas system for heating, but the cost of ownership must consider multiple energy metrics. I was curious to understand the impact on various building energy profile metrics associated with a Dedicated Outdoor Air System (DOAS) using the conventional gas fuel source vs. the latest VRF heat pump technology using electricity in a multifamily building. The findings of this investigation challenge the deep-rooted notion that electricity, being more expensive than natural gas per BTU, will always cost more to operate.

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Trends in Healthcare: Charging Stations

Trends in Healthcare” is a recurring series that focuses on exciting new designs and technologies we’re seeing in healthcare projects and provides best practices on how to ensure that these latest trends are accessible to persons with disabilities. We build on the wealth of knowledge we gain from working with healthcare design teams, construction crews, and practitioners to provide practical solutions for achieving accessible healthcare environments.


Anyone who has ever had to take a trip to the hospital knows how much time is often spent in the waiting room. As a result, our experience in that space can shape our perception of the entire visit. In fact, studies have shown that a visitor’s impression of the waiting room itself contributes significantly to the likelihood of a return visit.[1]  The length of wait times can vary – from a relatively short wait for a screening, to an average of 40 minutes in emergency departments, to the better part of a day if you are waiting for a family member to receive treatment.[2] As healthcare providers strive to remove pain points within the patient experience, they are turning to a number of design strategies to help create a more pleasant waiting room experience. One of these strategies is to ensure that patients and visitors have access to electrical outlets.

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Tech Notes: Automatic Doors

image of "Caution Automatic Door" signAs the country continues to confront the realities of the COVID-19 pandemic, the way we navigate spaces is changing. One of these changes is the way we interact with common use objects that traditionally require hand-operation, like doors. While automatic doors have always been a good option for providing greater access to people with disabilities, hygiene concerns associated with the spread of disease have presented another argument for their use. The rise of touchless technology as a result of this pandemic will increase the use of automatic doors not just for accessibility or convenience, but for public health as well. For anyone considering incorporating automatic doors into their designs, either for new construction or as a retrofit, here are some important things to consider:

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How to Talk Windows with a Passive House Nerd

Before we get into this topic, please take a few seconds to consider the following questions:

  • Do you plan to work, or have you ever worked, on a Passive House building? (If not, the rest of your answers are probably no.)
  • Has your Passive House consultant ever told you that the window U-Value you provided “won’t work in their energy model?”
  • Has your Passive House consultant ever told you that your window “doesn’t meet the comfort criteria?”
  • Have you ever scratched your head when someone asked you to provide the “Psi-spacer” for your window?

If you answered yes to two or more of these queries, please read on. If not, you’ll still learn some useful information, so why not continue?

If you’re still reading, then you are probably somewhat familiar with a “U-Value” and you may know what “SHGC” means. If not, no worries. This article will explain both, and by the end you’ll be able to talk about these terms with most Passive House nerds.

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Tech Notes: Door Surface

The 2010 ADA Standards and the A117.1 Standard for Accessible and Usable Buildings and Facilities require the bottom 10 inches on the push side of a door to be smooth and free from any obstructions for the full width of the door. While there are some exceptions (e.g., sliding doors or tempered glass doors without stiles), this requirement applies at the following locations:

  • 2010 ADA Standards:
    • Public and Common Use Areas: All doors along the accessible route
    • Accessible Dwelling Units: The primary entry door and all doors within the unit intended for user passage
  • A117.1 Standard:
    • Public and Common Use Areas: All doors along the accessible route
    • Type B Dwelling Units: The primary entry door
    • Type A and Accessible Dwelling Units: The primary entry door and all doors within the unit intended for user passage

The door surface provision is intended to ensure the safety of people with disabilities who require the use of a wheelchair, walker, cane, or other mobility aid. It is common to utilize the toe of the wheelchair or leading edge of another mobility device to push open a door while moving through it. The smooth surface allows the footrest of a wheelchair or other mobility device that comes into contact with the door to slide across the door easily without catching.

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Whole Building Blower Door Testing – Big Buildings Passing the Test

The residential energy efficiency industry has been using blower door testing since the mid 1980’s to measure the air tightness of homes. Since then, we’ve evolved from testing single family homes, to testing entire apartment buildings. The Passive House standard requires whole-building testing, as will many local energy codes, along with assembly testing. While the concept of – taking a powerful fan, temporarily mounting it into the door frame of a building, and either pulling air out (depressurize) or pushing air into it (pressurize) – is the same for buildings both large and small, the execution is quite different for the latter.

Commonly called a whole-building blower door test, we use multiple blower doors to create a pressure difference on the exterior surfaces of the entire building. The amount of air moving through the fans is recorded in cubic feet per minute (CFM) along with the pressure difference from inside to out in pascals. Since the amount of air moving through the fans is equal to the amount of air moving through the gaps, cracks, and holes of the building’s enclosure, it is used to determine the buildings air tightness. Taking additional measurements at various pressure differences increases the measurement accuracy and is required in standards that govern infiltration testing. Larger buildings usually test at a higher-pressure difference and express the leakage rate as cubic feet per minute at 75 pascals or CFM75.

Image of SWA staff setting up blower door test

SWA staff at a project site setting up a blower door test

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Electric Cars: Are They Better for Your Pocket and the Climate Right NOW?

Last week, I read a blog post from Connecticut Fund for the Environment President Curt Johnson, and he reaffirmed what I already expected: my next car will likely be an electric vehicle (EV). I currently drive a Toyota Prius hybrid, but when I bought it in 2013, the price to purchase and to operate an EV did not work out, so I chose the Prius, which has very reliably achieved 50 mpg over the last six years.

As an engineer who admittedly knows nothing about cars, I feel like the information out there on EVs is either slightly biased (i.e., published by EV manufacturers) or not transparent enough with the math to convince me. So I set out to create a blog post that was unbiased and transparent. I liked this one from Tom Murphy, an associate professor of physics at the University of California, San Diego, so hopefully I’m making it a bit more user-friendly and applicable to your current/local situation.

I just wanted to know two simple things (and admit to ignoring a long list of other factors that influence the type of car most people will choose to drive):

Number 1: At what gas price is an EV cheaper to drive per mile?

Number 2: While EV tailpipe emissions are zero, is my local electric grid clean enough that it’s a good idea, right NOW? I know my next car will be electric, I just don’t know WHEN the grid will be clean enough that it’s better for the environment for me to switch.

When I began writing this article, I had no idea what the answers would be.

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Tech Notes: Accessible Parking in Precast Garages

When designing accessible parking spaces, it is important to remember that the slope of the ground surface for the entire parking space and adjacent access aisle must not exceed 2% in any direction. We frequently see noncompliant slopes at accessible spaces, especially when the ground surface is asphalt or permeable pavers.  The slope along the perimeter of spaces at curbs or gutters is frequently more than 2% at up to 5%, which requires careful detailing and planning on the part of the architect, civil engineer, and on site contractors to ensure that a compliant slope is achieved at the accessible parking spaces. At parking structures and precast garage systems, we have found that important details and coordination needed to achieve compliant ground surface slopes are often overlooked.

 

Ground surface slopes at walls or parapets often exceed 2%, (blue highlight) resulting in noncompliant slopes at the heads of accessible parking spaces.

In parking structures, it is common for an area along the perimeter of the slab (adjacent to walls or parapets) to slope in excess of 2% for drainage purposes. In some cases, this slope is embedded into the precast system. As a result, accessible parking spaces must be located away from the sloped edges during the initial design phase.

In other cases, noncompliance results from the application of a cast in place (CIP) wash applied to the top of the precast slab. In the detail shown below, note the slope condition at the CIP topping. The wash is often indicated only in section details on the precast drawing set, making it easy to miss if designers are not specifically looking for how these details affect accessible parking spaces. The entire project team involved in the design and/or construction of the garage must be made aware of where accessible parking spaces are located and understand the specific slope requirements to ensure that details are properly coordinated.

The cast in place topping results in a slope of more than 2% at 8.33% at the head of the accessible parking space in this precast garage.

 

Once the garage is constructed, it is nearly impossible and very costly to fix noncompliant slopes at the head of accessible parking spaces. In some garages, we have been able to solve the problem by shifting the striping at accessible parking spaces. This results in the steeply sloped ground surface being located fully outside of the parking space and access aisle. The problem is that this solution is dependent upon whether the spaces can be shifted without compromising the minimum required width of the drive aisle or obstructing access to other parking spaces.

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Trends in Healthcare: Nurse Call Devices

“Trends in Healthcare” is a recurring series that focuses on exciting new designs and technologies we’re seeing in healthcare projects and provides best practices on how to ensure that these latest trends are accessible to persons with disabilities. We build on the wealth of knowledge we gain from working with healthcare design teams, construction crews, and practitioners to provide practical solutions for achieving accessible healthcare environments.


According to the U.S. Centers for Disease Control and Prevention (CDC), falls account for 3 million injuries treated in emergency rooms, 800,000 hospitalizations, and 28,000 deaths each year in the U.S. One in five falls cause serious injuries such as concussions/traumatic brain injuries and hip fractures. Not only is this a public health concern, it is extremely costly. According to the CDC, medical costs directly related to injuries resulting from falls totaled more than $50 billion in 2015.[1] Within hospitals and long-term care facilities, effective implementation of interventions and design strategies to reduce patient falls are key to increased patient safety and decreased medical costs. However, it may not be possible to eliminate patient falls altogether, so features like a properly installed nurse call system can be life changing.[2]

Accessible Nurse Call Stations

Most state and local standards and regulations require nurse call devices in each public toilet room and within inpatient bath, toilet, and shower rooms.[3,4] Where provided in spaces required to be accessible, the nurse call device must also be accessible. An accessible nurse call device is one that meets the following requirements:

  • All operable parts, including call reset switches, are within accessible reach range (15-48″ AFF);
    • NOTE: Determining compliant mounting height requires coordinating with the location of operable parts on the specific model used.
  • Operable parts do not require tight grasping, pinching, or twisting of the wrist to operate; and
  • Operable parts can be activated with no more than 5 pounds of force.

The location of operable parts differs between models of nurse call devices. It is important to determine mounting location based on the specific model of device being used.
Models shown (clockwise, L to R): Intercall Emergency Stations; Becas BeSmart Nurse Call System; Cornell Visual Nurse Call System

While these criteria appear straightforward, proper placement of nurse calls can become complicated when coordinated with minimum grab bar clearances and additional requirements under FGI, NFPA 99, NFPA 70, Ul 1069, UL 2560, and other local codes.

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Establishing Moisture Control in Multifamily Buildings

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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