Party Walls

*click here to read Part 2 of this blog

Project teams pursuing Passive House frequently ask, “Where do we locate the HRV/ERV?” The answer is complex when the Passive House concept is scaled to a multifamily program.  While there are two primary arrangements for HRV/ERV systems, the trade-off is dynamic and needs to be carefully considered as multifamily Passive House projects begin to scale. A low volume HRV/ERV unit ventilating an individual apartment is a unitized HRV/ERV. High volume HRV/ERV units ventilating multiple apartments and often servicing several floors, is referred to as centralized HRV/ERV.

As Passive House consultants we can attempt to address the system arrangement question with building science; however, in New York City rentable floor space is very valuable, so considering the floor area trade-off is of particular interest to project teams. When a unitized HRV/ERV system cannot be located in a drop-ceiling due to low floor-to-floor height, it is placed in a dedicated mechanical closet. This closet is typically no smaller than 10 ft² and includes the necessary ductwork connections to the HRV/ERV unit. The alternative solution is to increase the floor-to-floor height to accommodate the HRV/ERV unit and horizontal duct runs in the ceiling. Centralized HRV/ERV systems, however, allow short horizontal duct runs but require floor space to accommodate vertical shafts. With supply and exhaust ducts coupled together the required floor area is about 8-12 ft². As a result, centralized HRV/ERV systems may actually require more floor area than a unitized system.

Example: In the case of Cornell Tech, vertical supply and exhaust duct work for the centralized HRV/ERV system required 222.5 ft² per floor, or 13 ft² per apartment (see image 1 below). Unitized HRV/ERV mechanical closets would have required an estimated 170 ft² per floor, or 10 ft² per unit (image 2 on right).

Image 1 & 2:  These images compare the amount of floor area required for centralized and unitized HRV/ERV systems. Image 1 on the left, shows the 12ft² floor area required for vertical shafts servicing the centralized ERV at Cornell Tech. Image 2 on the right is hypothetical, showing the typical location and 10ft² floor area required for a unitized HRV/ERV mechanical closet.

(more…)

Steam pressure gets a disproportionate amount of attention. That’s partially due to the common, but not necessarily true idea that higher pressure equals more fuel use. Remember, it’s not the steam’s pressure that heats the building; it’s the steam’s heat energy. In fact, you can heat a building with 0 psig steam. You can even heat a building with a boiler that’s too small and never builds positive pressure. You can’t do it well, but you can do it.

System Operation

Thanks to the law of conservation of energy, we know that energy cannot be created or destroyed — it can only be altered from one form to another. In a steam heating system, the flow of energy goes like this:

1. The boiler transfers Btus from the fuel to the steam (energy input).
2. The steam transfers those Btus to the rooms.
3. The rooms transfer those Btus to the outdoors (heat loss, aka the load).

It’s important to keep this energy flow in mind because they are linked and self-equalizing. If the energy input exceeds the heat loss, the building temperature will increase, which, in turn, increases the heat loss. And, a building’s heat loss depends on the temperature difference between inside and outside and the amount of air transfer occurring. So, the best way to keep the heat loss down is to keep the indoor temperatures as low as possible, and keep the windows closed. Furthermore, in an apartment building, the coldest room drives the load in any steam-heated building and the Super needs to send enough heat around to satisfy the hardest-to-heat apartment.

(more…)

Over the past several years, as the desire for more sustainable and environmentally friendly transportation has increased significantly, we have been seeing a corresponding increase in the number of electric vehicle charging stations provided in parking lots and garages. Applicable federal, state, and local accessibility laws and building codes may not specifically address how to make these charging stations accessible, but that does not mean they are exempt from compliance. Under most regulations, where electric charging stations are provided, at least one must be accessible.

But what does an accessible charging station look like?

(more…)

Residential ventilation is really a tricky topic. But if you’re looking for a practical, cost-effective, holistic solution, go somewhere else. This post offers none.

Hopefully I can dig into practical solutions in future posts, but I think it’s important to be clear about why we ventilate and what an “ideal” ventilation system might look like in a new, efficient home. My ideal system is similar for both single-family or multi-family (though practical issues can be very, very different).

Purpose of ventilation: Remove contaminants that can compromise health, comfort, productivity, durability, etc. I’m sure there are more rigorous definitions out there, but this will work for now. There are other ways to lower contaminant levels:

• Emitting fewer contaminants from materials and activities is obviously good. Do this.
• Actively filtering, adsorbing, or otherwise removing contaminants from indoor air can also be good. There’s talk about doing more of this, but I’m tabling it for this discussion. This may be something to keep an eye on down the road.

For most new residential buildings, mechanical ventilation is still be the primary means to remove contaminants. Or at least it’s the primary method that designers/developers need to plan for now.

If building a new, efficient home in Shangri-La, my ideal ventilation systems would look like this: (more…)

Here’s a question that we’re often asked by our clients: “I’m building a new residential building, should I use LEED for New Construction (NC) or LEED for Multifamily Midrise (MFMR)?” The answer isn’t exactly simple, especially with the introduction of new credit requirements in LEED v4 and the fact that USGBC allows project teams to choose between the two rating systems. Ultimately, it will come down to a difficult decision based on the goals and final design of the project. So, in an effort to help clear up the confusion and possibly make the decision a little easier for you, we decided to break down a few scenarios that highlight key differences between the rating systems that may not be apparent upon first glance.

In our first installment, we took a look at a four story multifamily building and highlighted many of the key differences between the rating systems; you can find that post here. In this edition, we will explore the options for a different building type.

(more…)

Whether you’re a Clark Griswold or an Ebenezer Scrooge, it’s that time of year again: the holiday season is upon us.

Even those of us who try to live a greener, more eco-conscious lifestyle have a tendency to abandon ship and surrender to the flow of unabashed consumerism and waste in the name of “just getting it done.” It’s hard to put added pressure on ourselves to be mindful of our environmental impact when there are gifts to be purchased, cards to be sent, stockings to be hung, and photos of dogs in Santa hats to be taken.

But you don’t need to do it all to have an impact.

Find one or two ways to improve your holiday traditions by making them greener. Perhaps pick the ones that justify you doing less work in the name of the environment (Reusable bags instead of gift wrap? Yes please). Think of it as a gift to Mother Earth or humanity, or as a way to further annoy that aunt who just can’t understand why on earth you would want use cloth diapers. Sigh.

Here are some ideas, tips, and tricks to help you be just a little more sustainable this holiday season:

(more…)

Our accessibility consultants are constantly on the lookout for improvements in product design that will make it easier for our clients to comply with accessibility criteria. As manufacturers become more familiar with accessibility requirements under applicable federal, state, and local regulations and building codes, a number of innovative, accessible products have emerged to make compliance simpler and more stylish.

Here are just a few examples of accessible products that we have been recommending recently…

(more…)

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.
(more…)

 

As the Passive House standard continues to make waves across New York City and the U.S., an entirely new design process has evolved to respond to the challenges of higher insulation levels, balanced mechanical ventilation, and perhaps the most difficult hurdle – an air tightness level that most would think is impossible. For the recently certified Cornell Tech building on Roosevelt Island, the tallest Passive House in the world, a several year-long coordinated effort was required to achieve such a feat. So what is the requirement, how is it measured, and what are the strategies and considerations required to achieve it?

(more…)

Many green building programs put a heavy emphasis on not only the sustainability of a building once it is built, but increasingly so on the sourcing and management of building materials in an environmentally responsible way. Sustainable Supply Chain (SSC), sometimes referred to as “cradle-to-cradle,” is the standard term to reference this process. But, what does it mean?

What is a Sustainable Supply Chain?

SSC embodies a cyclical approach to manufacturing that considers both the recovery and reuse of materials. This supply chain’s reverse logistics strives to continually sustain itself by returning materials to the land in either a safe molecular form or by continually reusing those materials for future products. Fully developed SSC’s consider sustainability for every contributor at every step – from design to manufacture, transportation, and storage to eventual end-of-life with a goal of re-use, recycling, or low impact disposal. This forward-thinking perspective serves to reduce waste, promote ethical and socially beneficial manufacturing practices, minimize or eliminate adverse health impacts, and enable compliance with increasingly stringent regulations. (more…)