Multifamily buildings can be a unique challenge when it comes to selecting effective heating and cooling systems. In the Washington, DC region’s mixed-humid climate, humidity control becomes a central challenge because of a couple inescapable realities.

1. There is a lot of moisture added per square foot from cooking, bathing and even just breathing due to the dense occupancy.
2. The small exterior envelope areas mean the air conditioner won’t kick on very often, and thus won’t have a chance to remove moisture.

High humidity can lead to complaints over comfort, condensation on registers and exposed duct work, and even mold. To effectively remove moisture, the air conditioner should run for long stretches. This means properly sizing mechanical system. Unfortunately many project teams exacerbate the problem by selecting grossly oversized cooling equipment that runs even less frequently.

Steps to Right-Sizing Mechanical Equipment

1. Perform accurate calculations using the Manual J process to estimate peak heating and cooling loads
2. Consult the manufacturer’s performance data at design conditions, and
3. Select the smallest piece of equipment that will meet the load.

Common Problems When Sizing Mechanical Systems

 “Can’t I just use the worst-case orientation?”

Large windows in a corner unit can change the equipment sizing needs compared to interior units

No. In most cases the largest envelope load in apartment units is the windows. A unit with floor-to-ceiling windows facing west will have very different loads than the same unit facing north, so be sure that the load calculation reflects the actual orientation. If the same unit type occurs in more than one orientation calculate the loads for each orientation and make selections accordingly. This may require different selections and duct layouts for different orientations.

“Can I use commercial software?”

Yes, but you have to be careful. Commercial load software like Train TRACE and Carrier’s HAP are primarily geared towards non-residential space types that have very different use profiles. For instance, in an office setting you would expect lighting and equipment to be 100% on during the peak afternoon cooling hours. However, in a residential setting few if any lights are on during the day.

The commercial programs also like to include more outdoor air than you actually see in apartments. A reasonably well-sealed apartment will have very little natural outdoor air infiltration (remember only 1 or 2 sides of the apartment “box” are actually exposed to outside) and mechanical ventilation should only be about 20-35 CFM depending on the size of the unit. It is not uncommon for loads to drop by half once those inputs are corrected.

 “Will small systems have enough power to get the air to all the rooms?”

Smaller systems don’t mean less power

Absolutely. First of all, the smallest split systems available are 1.5 tons, which is really not that small. Second of all, 1.5 tons air handlers are rated to 0.5 IWC external static pressure just like 2 and 2.5-ton systems. If that sounds like gibberish it means 1.5 ton systems have the exact same “power” to push air through long runs as larger systems.

The blower motor is smaller only because it’s pushing less air, just like a motorcycle has a smaller engine than a car but can still accelerate as quickly. We have seen 1.5 ton systems used in 1500+square feet  2-story homes. If you can’t get air to a 900 square foot apartment you have a duct sizing issue, which would be a problem no matter what size the air handler.

 “Doesn’t each room need 100 CFM of airflow for comfort?”

Well, maybe. Is 100 CFM what the load calculations show is needed? There is no such thing as a minimum airflow threshold for each room. The amount of air required is in direct proportion to that room’s heating and cooling load. If the calculations show a small load and only 40 CFM required you should supply 40 CFM. In fact, oversupplying 100 CFM will actually cause discomfort since that room will always be a few degrees off from the rest of the apartment. Sitting under an oversupplied register could be loud and drafty as well.

“But can’t I just size by bedroom count?”

No, rules of thumb don’t cut it anymore. For buildings built to 2009 or 2012 code in our climate zone (CZ4), most apartment units will have loads less than 1.5 tons, no matter how many bedrooms. There may be a few 2-ton or (rarely) 2.5-ton systems for larger apartments on the corner or top floor, but those are the exception.

If your mechanical plans show 1.5 tons for all 1 bedrooms and 2 tons for all 2 bedrooms it probably means

1. Accurate sizing procedures were not followed, and
2. A lot of those 2 bedrooms actually only need 1.5 ton systems

The only way to know for sure is to perform the calculations.

Conclusion

Most of these issues are the result of a very natural instinct to be conservative in the face of uncertainty. The truth is there are a lot of variables that will change the real-world heating and cooling load in a unit: how many people are in the apartment, when they are cooking, are they using blinds. The problem is in this case “conservative” means designing for temperature control at the expense of humidity control. Every extra ½ ton capacity means less dehumidification – that’s a fact. The only way to control both temperature and humidity is to perform accurate calculations, resist the urge to add extra safety factors, and size the equipment strictly according to the calculated loads.

As an added benefit, smaller equipment requires smaller electric service capacities. Especially in a rehab situation with existing service, choosing right-sized equipment is more likely to allow the use of existing service instead of requiring expensive service upgrades.

The post Getting it Right – HVAC System Sizing in Multifamily Buildings appeared first on Everyday Green | Green Homes and Energy Efficiency.

The Washington Post sought homeowner driven LEED Homes projects for a recent article, and they landed on three homes in the Washington, DC region. Two were projects Everyday Green supported, both of which are architect – owners, Todd Ray’s home in Arlington, VA and Erik Hoffland’s home in Washington, DC.

Everyday Green was the rater for the Ray’s LEED Homes Platinum, NGBS Gold, Indoor airPLUS and ENERGY STAR version 2 certifications. As the article points out, Todd wanted to compare the programs for the benefit of his staff. But third-party certification isn’t just about pushing paperwork. Required third-party inspections by Everyday Green revealed some necessary tweaks to get all the green systems working and in compliance with the standards.

Learn more about the Ray’s certification process for their Arlington, VA home and how Everyday Green’s commissioning process:

• Identified critical insulation corrections where sections of the addition were meeting with the existing home
• Configured ventilation system and controls for effective fresh air distribution
• Discovered close to $200 / yr in water and energy savings from a faulty showerhead.

In the Washington Post LEED Homes article, Erik Hoffland rightly notes LEED Homes certification is about the process, not just the points. He used the the checklist as a guide for what to consider to make his home greener and more sustainable. While his home is still waiting for a final re-inspection, Everyday Green’s testing helped reveal leaky ductwork to be fixed that will help with temperature disparities between floors.

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From an insurance carrier’s perspective, building a green home equates to building a safe home. The home is better able to withstand harsh weather and other perils that are a common cause of claims. For homeowners this means qualifying for more preferred insurance policies and therefore paying less to insure their property.

When green home building was still in its infancy, the notion that building “green” was more expensive required many homeowners to purchase an endorsement on their homeowners policy to cover any additional costs incurred by the insurer. According to a study performed in California by Davis Langdon, Inc, building green costs only about 2% more than conventional construction. So while many insurers still require this endorsement, they are helping to counteract that additional cost to homeowners by implementing a discount for LEED certified homes that typically knocks about 5% off of the premiums after all other factors have been taken into consideration. This is great news for green home owners, but it doesn’t stop there.

Certifications, discounts and endorsements aside, some green home features qualify a homeowner for better insurance policies automatically. Following are some of the ways green construction is safer – and therefore presents less risk for owners and insurers:

Materials Matter

The same upgrades to your roof that can help win certification for your home often also can help it stand up better to fire, wind and hail. Those are some of the most damaging problems and often result in major payouts for insurance companies. Therefore, homes built with new, durable roofing materials often qualify for a preferred homeowners policy that requires lower annual premiums.

The Pipes Aren’t Calling

Green homes generally are built to use less water – LEED certification requires at least 20% water savings – than conventionally built homes. Why is that important to insurance carriers? Because water damage, often from damaged pipes or plumbing fixtures – is another source of major claims. Updated plumbing systems means there’s less danger of a broken pipe or other problem, again qualifying homeowners for better rates.

Losing the Fire is a Good Thing

Did you know there are about 500,000 structure fires in the U.S. every year according to the National Fire Protection Agency? Problems with outdated electrical and air conditioning systems often are to blame. By contrast, green-certified homes typically feature electrical and air conditioning systems designed not only to use less energy but do to it safer than a non-energy efficient product. That means lower risk for home insurance providers and, likely, lower premiums for the people who insure sustainable homes.

The Discount Factor

Having efficient plumbing, HVAC and roofing are just a few ways that green homes automatically qualify the homeowner for better rates. In addition, many carriers now offer a LEED Discount for LEED-certified homes averaging 5% off of the premiums after all other factors have been taken into consideration.

Architects, developers and contractors undertake green projects because they’re important to the end user – homeowners who care about sustainable lifestyles. The fact that greener buildings also are safer buildings and cost less to operate are added benefits, as are the lower insurance costs that can accompany sustainable living.

Green building owners who are interested in learning more about potential savings on their property insurance should contact their current provider and be prepared to supply proof of certification.

This article was contributed by Carrie Van Brunt-Wiley, Editor of the HomeInsurance.com blog. Carrie has been writing insurance news and consumer information for HomeInsurance.com since 2008. HomeInsurance.com serves as an open consumer marketplace and a resource for property and casualty insurance data.

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For decades code has required all plumbing pipes in a house be pressure tested. We expect plumbing to be 100% leak free and for good reason. However when it comes to duct work there is on average 25% leakage occurring. This not only wastes huge amounts of energy but can also lead to comfort complaints, moisture problems, mold, and rot because leaky duct work brings moist air in through attics and crawlspaces.

With the 2009 International Residential Code (IRC) duct work located in attics or basements must now also be tested for leaks.  The bulk of this new requirement is falling to HVAC contractors. Change is hard and we’ve noticed a trend when working with HVAC contractors new to reducing duct leakage – old habits die hard – and like any grieving process there are 4 stages to duct leakage failure.

Step 1)  Denial

“There must be something wrong with your duct blaster equipment or maybe you’re not doing the duct leakage test right?”

A duct blaster is attached to the return grill to measure duct leakage

Duct leakage is different from a plumbing leak in that it’s pretty obvious to everybody when a pipe is leaking water. Duct leakage goes unnoticed unless diagnostic testing is performed. All of Everyday Green’s technicians are HERS Raters. The gauges we use to measure leakage must be factory calibrated every 12 months per RESNET Standards. HERS Raters also have to pass a proctored field exam demonstrating proper use of the equipment to become certified and are subject to annual 3^rd party oversight in the form of Quality Assurance checks by a RESNET Accredited Provider Organization. All of these standards are in place to ensure tests are replicable no matter who is performing the test.

Step 2) Anger

“I have been installing duct work for 20 years and I know I sealed every joint”

This duct has mastic on the bottom but on top is completely unsealed.

A liberal coating of duct mastic works best to seal seams and make connections. A good rule of thumb is to make the mastic as thick as a nickel. Sometimes site conditions make it difficult to get every joint, especially if it wasn’t sealed on the floor in sections and then put into place where connections are accessible for sealing. Sealing the leaks closest to the air handler and plenum will result in the biggest energy savings. Remember “Boots for show, plenum for dough.”

Step 3) Bargaining

“Well now that you mention it, there is this tricky area I couldn’t quite get to because of this beam. Can’t you just pass this house and we’ll do the next one better?”

Duct work needs to be sealed tight in every home, especially when ducts are running through unconditioned space. Leaky ducts in both conditioned and unconditioned space contribute to rooms being too hot in the summer or too cold in the winter because not enough conditioned air is making it to the rooms. In winter leaky ducts can contribute to condensation forming in attics and crawl spaces. Mold can quickly follow as the warm moisture-laden air is driven into the cold spaces.

Step 4) Acceptance

Seeing is believing and during a mid-construction inspection Everyday Green’s raters can pump theatrical fog into the ducts with the same fan used for testing. This allows the contractor to see where the ducts are leaking as well as what opportunities exist to make repairs.

Duct leakage numbers are reported as percentage of leakage per conditioned square footage. So when a technician reports a system has 6% leakage in a 2500 sq. ft. home they have measured 150 cubic feet per minute (CFM) of air being drawn through their calibrated fan and into the duct system at a standard pressure difference of 25 pascals or 0.10 inches of water column which is a typical pressure the ducts would be under during normal operation.

Duct Leakage Requirements

Once HVAC contractors reach the acceptance stage, they readily adopt new practices to ensure tight duct work. One of the biggest culprits of duct leakage is at the equipment itself, below are some good details for how to properly seal around the mechanical system.

The post Four Stages of Duct Leakage Failure appeared first on Everyday Green | Green Homes and Energy Efficiency.

The ENERGY STAR New Homes certification is broken into three main sections:

1. HVAC system design and installation
2. Thermal Enclosure
3. Water Management and Durability

These features must be verified by qualified HERS Raters like Everyday Green’s team of raters.

The below video walks through the benefits of living in an ENERGY STAR certified home with feedback from the homeowners who live in them.

Proper design and installation of the heating, cooling, ventilation and exhaust systems.

High–efficiency systems are engineered and installed to deliver more comfort, better moisture control, improved indoor air quality, and quieter operation. Learn more about a complete heating and cooling system in this fact sheet.

• The heating and cooling system has been engineered and installed to efficiently deliver comfort. Proper sizing of equipment and ductwork is essential to achieving optimum home performance and comfort.

Everyday Green’s team will work with your engineer or HVAC contractor to get the calculations and design done properly before any equipment is ordered. Our reviews often result in right-sizing of equipment and saving money by installing smaller systems than originally designed.

• A constant supply of fresh, filtered air is provided, reducing indoor pollutants, dust, pollen, and other allergens.

Everyday Green specializes in understanding whole house ventilation systems. While the details are new to many engineers, architects and general contractors, we’ve worked designing and verifying mechanical ventilation systems for over 200 projects.

• Consistent temperatures are felt across every room, making the entire home comfortable year-round.

Effective Thermal Enclosure

Comprehensive air sealing, properly installed insulation, and high–performance windows work together to enhance comfort, improve durability, reduce maintenance costs, and lower monthly utility bills. Learn more about the benefits of a complete thermal enclosure.

• Air Sealing - a typical home contains a half-mile of cracks and gaps behind walls and around windows and roods, along with dozens of holes for pipes, vents, ducts, lighting, and wiring. Sealing these openings with a comprehensive air sealing package helps to significantly reduce drafts, moistures, dust, pollen, pests and noise.

Everyday Green inspections are tailored to find gaps in air sealing and get them corrected before drywall is hung. We can even perform a blower door infiltration test mid-construction to find any pathways air may be leaking into your home.

• Properly Installed Insulation – It’s not just the amount of insulation; it’s the quality of installation that makes all the difference. Proper installation includes careful placement to eliminate gaps, voids, and compression; complete air barriers that prevent air from bypassing the insulation; and building techniques that minimize heat flow through framing. This ensures consistent temperatures throughout the house, reduced energy use, and increased comfort.

Everyday Green’s inspections uncover on average of 10 corrections for the typical custom family home when it comes to properly installed insulation. Make sure these errors are found in your next project.

Water Management and Durability

Tried–and–true building practices, such as flashing, moisture barriers, and heavy–duty membranes, are employed to effectively drain water from the roofs, walls, and foundations of ENERGY STAR certified homes. Learn more about the Water Managed Assemblies features.

Get Started with ENERGY STAR

Everyday Green’s raters will walk you through the ENERGY STAR New Homes process from start to finish. Download the verification checklists and contact us to get started on your new home or multifamily building certification today.

The post ENERGY STAR for New Homes appeared first on Everyday Green | Green Homes and Energy Efficiency.

The National Institute for Standards and Technology (NIST) Net Zero Energy Residential Test Facility in Gaithersburg, MD won the Environmental Benefit category during the 8th Annual USGBC Maryland Wintergreen Awards for Excellence. The home is a living laboratory of building science and is being used by the Building Environment Division at NIST to research performance, indoor air quality, energy efficiency and the viability of net zero homes.

The home has multiple systems allowing for reconfiguration of mechanical systems, solar thermal and solar PV systems as well as future incorporation of smart grid technologies. The home even comes complete with a mechanical family to simulate occupant usage. The home is getting to net zero with extensive continuous insulation, advanced framing, significantly reduced infiltration and solar PV among other strategies.

The NIST Net-Zero building earned LEED Homes Platinum, ENERGY STAR version 3 and Indoor airPLUS certifications with Everyday Green serving as the rating organization and LEED Homes Provider. Everyday Green performed onsite inspections and testing, and helped the project team bring duct leakage from over 700 CFM throughout the system down to 315 CFM to meet performance testing requirements. Everyday Green also helped the project team properly size the multiple mechanical systems and configure the ventilation controls.

More information about the project and ongoing research can be found on the NIST website.

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