Noel's Green (make that SUSTAINABLE) Blog » Energy Performance Contracting

The bottom line! Building commissioning today

noel — Mon, 11 Jan 2010 01:13:04 +0000

I would like to share this 2006 excerpt from the Building Design and Construction magazine white paper on the bottom line of building commissioning.

To put some solid numbers on benefits of commissioning, Evan Mills, PhD, and colleagues at Lawrence Berkeley National Laboratory, Portland Energy Conservation, and Texas A&M University (Energy Systems Laboratory) reviewed published and unpublished data on 224 buildings in 21 states, representing 30.4 million sf of commissioned space—73% in existing buildings, 27% in new ones. Total commissioning costs for these buildings were $17 million (2003 dollars), an average $0.55/sf.

Among their findings:
■ An average 11 deficiencies were found in existing buildings, 28 in new buildings. HVAC systems represented the bulk of the problems.
■ For existing buildings, median commissioning costs were $0.27/sf; energy savings came to a median 15% (18% average); payback times were less than nine months (0.7 years).
■ For new buildings, commissioning costs were $1.00/sf (0.6% of total construction costs), yielding a median payback of 4.8 years.
■ Reduced change orders and other non-energy benefits accounted for $0.18/sf savings in existing buildings and $1.24/sf for new construction— “comparable to the entire cost of commissioning,” the researchers note.

The authors conclude that “commissioning is one of the most cost-effective means of improving energy efficiency in commercial buildings.” While not a panacea, they admit, it is “one of the most cost-effective and far-reaching means of improving the energy efficiency of buildings.”

Post-occupancy evaluations can help property owners, developers, and AEC firms determine how buildings are functioning for tenants or occupants.

What can I add to this? Implementation and testing YOUR PROJECT. CALL ME TODAY for a no-cost evaluation

Building Air Leakage and Air

noel — Sat, 12 Sep 2009 14:20:19 +0000

I just love this subject. Do you know whether your building is sucking or blowing? Did you know that even a new building, built to the usual building methods, will leak air? In a new project, the key is to make allowance for that, and design, build and validate accordingly. On an existing building, it is important to determine how much and where your building blows or sucks, so you can take action, if need be. Windows, doors, and construction joints all have a normal tendency to leak air or allow infiltration. Varying pressures within the building and across each envelope, causes air to move through these openings.

blower door

“Blower door” tests are a key tool for determining how much leakage occurs and in which direction, in (negative pressure) or out (positive pressure).

The major issues surrounding air leakage are indoor air quality, compromised comfort due to drafts or uneven temperatures, and energy usage. A good HVAC designer will account for all of these, and assure that undesirable effects, such as sucking cold or hot-humid in through the building joints is prevented. Likewise, a good architect/builder will account for the behavior of the envelope assembly, air leakage being but one behavior, in his/her design. (You can’t have a 100% tight envelope in practice, it rather more expensive to achieve 0% infiltration, so we plan for it, and plan to blow rather than suck. This rule does NOT apply to “clean rooms”, of course, where 0% infiltration is mandated.)

Blower door testing is a key component of new building commissioning or re-commissioning an existing building. If you know where all the intakes, exhausts, and door openings are, and their size and type, and then the remainder (theoretically) is the “tightness of the building’s construction”.

So building HVAC systems are commonly designed to create a slight positive pressure (blowing) at all times, to CONTROL infiltration. Design should always include some common sense and experience. ANSI/ASHRAE 62-2004, Ventilation for Acceptable Indoor Air Quality (IAQ), is the most commonly adopted code the prescribes indoor air quality and ventilation rates. The input of the ventilation code rules, combined with a input of air leakage rates, will guide the decisions on course of action.

Common reasons for buildings that suck and are uncomfortable include

obsolete HVAC controls,
building usage changes over time,
Increasing complexity of tenant build-out without corresponding update to HVAC
Increasing demand and complexity of schedules not adaptable to existing building
Increasing technological demand ( ie growing data communication rooms) not well integrated with the buildings older existing controls.

Solutions to these problems include

Periodic recommissioning of the HVAC systems and controls
Upgrading the HVAC controls
Sometimes existing building systems are just waiting to be replaced with simpler systems.

Many of us experienced energy modelers have been reliant on spreadsheets and/or dedicated heating and cooling calculation programs from the beginnings of our careers. But these methods are labor intensive and lately, we look more and more to BIM to help accelerate its use, or sometimes we are being required.

TECHNICAL POINT: How to model the air leakage in a building information model has been problematic up until very recently , I think. The recent releases last spring of new Revit add-ons (see the BIMOLOGY link to the right to read about ECOTECT ) give us some hope. I think that they are finally getting the details into the model. I could be wrong. But ideally it would be nice to specify and analyze air leakage across geometric boundaries on the fly.

In the end, its better to have a building envelope that blows a little, than a building that sucks at all.

ASHRAE 62-2001 synopsis on Internet(out-of-date in the exact details, so be careful)

Energy Engineering for your world

noel — Sat, 12 Sep 2009 05:13:04 +0000

Noel Susskind, PE, LEED AP is an experienced mechanical engineer and building energy expert ready to
serve you. Commercial, government, educational and healthcare facilities are a focus.
He will:

Serve as a high level resource on the latest science and art of building, or introduce you to one. Knowledge includes minimizing building energy (carbon) footprint via energy recovery, advanced control approaches , daylighting design, indoor air quality, ventilation, cogeneration, photovoltaic systems, etc.
Recommend energy-efficient design solutions and technologies, including lighting, HVAC, building envelope measures and passive solar and ventilation measures.
Validate and summarize energy audits of existing facilities by third parties.
Identify various alternative energy conservation measures and predict energy usage based on energy modeling. Includes economic analysis and financial projections with payback.
Work with the design and construction teams, sharing and validating others energy models (compliant with DOE-2 and BIM GbXML) as third party reviewer.
Provide documents and regular verification required for obtaining LEED energy credits.
Work closely with you on alternative solutions for building and system energy usage.