2018 has been a year to remember for SWA’s Party Walls blog. Our consultants have shared their passion for high performance buildings by recounting stories from the field and providing information, new findings, and best practices to improve the built environment.
Whether discussing topics based in New York City or Southeast Asia, here are our fan favorites from 2018…
Installing a dedicated domestic hot water (DHW) plant is a common energy conservation measure (ECM) in the New York City multifamily market. According to Local Law 87 data, approximately 80% of the audited multifamily floor area uses steam heating boilers to produce domestic hot water.[1] A recent SWA analysis of data from steam buildings with tankless coils that implemented this ECM suggests that auditors may want to think twice about recommending this measure widely.
Two unsupported arguments are typically made in favor of installing a dedicated DHW system.
Welcome back! In Part One we talked about how steam pressure gets too much attention. Controlling pressure for its own sake should never be the end goal—steam pressure is just a means to an end. In this post we’ll discuss one way that controlling steam pressure can be useful—where it can help you balance the system, control the temperature, and yes, save energy.
The biggest issue plaguing two-pipe steam heating systems are steam traps. Steam traps are supposed to do just that—trap steam—keeping the pressurized steam on the supply side of the system and allowing air and water (i.e., condensate) to pass through into the returns. Keeping the supplies and returns separate is critical, but steam traps are too failure prone to accomplish this reliably.
Radiator steam “trap” failed open
At the start of any heating cycle, the system is full of air, which must be removed for steam to enter the heaters. In most two-pipe systems, the steam pushes the air out of the heaters, through the traps, and into the return piping where it eventually exits the system through a vent in a vacuum or condensate tank. That’s what happens when the traps are working. But a failed open trap is no trap at all. It lets the steam flow into the return piping and, with pressure on both the supply and return sides, air is trapped in the system. This affects those farthest from the boiler—the heaters near the ends of the mains and on the top floors—the most. (And with air trapped inside keeping the metal cold, are they even heaters?)
So in utility and policy circles, electrification is all the rage. Grid electricity is getting cleaner (i.e. resulting in lower CO2 emissions), on-site renewables are taking off (sometimes even with storage), and heat pump technologies are getting better. More regional and utility initiatives are encouraging building owners/designers/developers to forego onsite fossil fuels entirely (or at least mostly) to help meet CO2 emission reduction goals. But is electricity really more sustainable than natural gas? Is it cheaper? Which is better, really?
Variable refrigerant flow (VRF), also known as variable refrigerant volume, was a concept developed by Daikin Industries in the 1980s. The technology is based on transferring heat through refrigerant lines from an outdoor compressor to multiple indoor fan coil units. VRF systems vary the amount of refrigerant delivered to each indoor unit based on demand, typically through variable speed drives (VFDs) and electronic expansion valves (EEVs). This technology differs from conventional HVAC systems in which airflow is varied based on changes in the thermal load of the space.
The two main VRF systems are heat pump systems that deliver either heating or cooling, or heat recovery systems that can provide simultaneous heating and cooling. These two applications, plus the inverter-driven technology of the outdoor compressors, allow for greater design flexibility and energy savings. In applications where heating and cooling are simultaneously called for in different zones, VRF heat recovery systems allow heat rejected from spaces that are being cooled to be used in spaces where heating is desired. (more…)
A few months ago I wrote about air-source heat pumps (ASHPs) in cold climates, and I promised more info on how to select the right systems and get the best performance. Below are some things we’ve learned from our work with ASHPs in the Northeast; much of this is based on the results from a study supported by the DOE Building America program. To be clear, we’re talking about inverter-driven (variable-speed) heat pumps in residential applications during heating season. Cooling is certainly important also, but we’ve been more focused on the heating performance, especially at lower temperatures. (more…)
Earlier this year, at the AHR Expo in Orlando, the biggest trade show for HVAC professionals, Aeroseal’s duct sealing technology was declared the Product of the Year, the top honor of the Innovation Awards. Aeroseal was recognized as “a groundbreaking solution to an industry-wide problem.”
The unique appeal of the Aeroseal technology is that it seals ducts from the inside. Walls and ceilings do not need to be removed or damaged to gain access for traditional mastic sealing. Aerosolized vinyl polymer particles from 2 to 20 micrometers are injected into a pressurized duct system. The particles stay suspended in the air stream until they reach the leaks, where they are deposited and built up at the leak edges until the leaks are sealed.
The Aeroseal technology has been around for more than two decades. It was developed at Lawrence Berkeley National Laboratory in the early nineties and patented in 1997. It has received many awards over the years including the Best of What’s New award from Popular Science magazine in 1996 and the Energy 100 award from the U.S. Department of Energy.
Whether code built or energy efficient, if your new home has a poured concrete foundation and floor slab, please pay particular attention to the following. While older, leaky homes result in low interior moisture levels (thus the desire for humidifiers on central furnaces); newer, tighter homes will typically have relative humidity levels in the 25-50% range naturally.
Moisture from construction materials in new homes must be managed to avoid problems like interior condensation and mold.
In some cases, there is a need to actually dehumidify to maintain relative humidity below 50% during the winter. In the first 1-2 years after the home is built, concrete foundations expel massive amounts of moisture as part of the concrete curing process called “hydration”. As the concrete cures, some of the water in the concrete mix reacts chemically with the portland cement and forms the hardened concrete, and some of the water evaporates to the surrounding air. The exterior water resistant/proof coating on the below grade portion of the foundation prevents moisture from escaping that way. Typically only a 1-2 foot tall area along the perimeter of the above-grade portion of the foundation is available for drying to the exterior. It is more likely that the moisture will be expelled to the interior of the home and therefore, must be managed to prevent deleterious moisture-related problems such as condensation, mold, wood rot, etc. Framing lumber also contributes: lumber that starts out kiln-dried at 18% moisture levels, will eventually end up at 6%.
How to deal with that moisture? Here is that cheap investment alluded to: an ENERGY STAR dehumidifier with a built-in humidistat. This unit should be plumbed to a drain to allow continual operation (without having the occupants empty a bucket). In addition, the dehumidifier should be installed in the basement or crawlspace as soon as the structure has been enclosed and power is available. In terms of the construction process, it is recommended that the foundation be the last item to be insulated to allow for the internal construction moisture to be removed prior to enclosing. After a year or two of occupancy, construction material moisture levels will become stabilized at “normal” levels. In the interim, remember to “build-tight and ventilate right”, but also manage that construction moisture.