Before the purchase of, or addition to any healthcare facility, you’ll need to consider both construction, design and installation factors to ensure the best possible indoor air quality.

Construction Issues

Before construction begins, make sure all new ductwork is sealed on both ends until it is installed. Unsealed ductwork on a jobsite will collect particulates that will contaminate your new HVAC system.

Never run the new HVAC system without air filters properly installed and all by-pass air around air filters eliminated. Construction debris, particularly sheetrock dust and saw dust, will be distributed throughout the new facility ductwork if the filters are not managed during construction. Many architects are now requiring that the air handling units and ductwork be clean before turning over the building.

Additionally, you’ll want to inspect the entire HVAC system for leaks. By-pass air around your air filters will immediately create indoor air quality issues. We ran a controlled experiment that showed a ¼ inch gap around a 95% high performance ASHRAE (MERV 14) worth about $100.00, will reduce the filter’s effectiveness to the performance level of a 30% ASHRAE (MERV 7) filter worth about $5.00. These leaks cause the HVAC system to be contaminated, which is very expensive to clean.

Perform commissioning to set standards that can be measured for future performance of HVAC equipment. Commissioning should also make sure HVAC equipment is performing properly and to make sure there is no bypass air around air filters and to make sure entire HVAC system is clean before occupation of building.

Filtration System Design

The design of the air filtration system is also important. For any construction project, you’ll want to ensure that the following factors are considered in terms of placement, safety, efficiency and code guidelines: Design all filter housings to be front loading, not side loading. Front loading housings are much easier to secure the air filters to prevent by-pass air, and they provide easier access for changing the filters.

Design the air filters for your air handling units to have at least 38 inches of clearance behind the filters which will accommodate most common air filters. Additionally, you’ll want to leave approximately 24-36 inches of clearance on either side of coils so they can be cleaned later. Also, make sure there are access doors in the air handling units to get to coils for cleaning.

We have found that staggered thin coils are better than one thick coil, as thick coils are very difficult to clean.

Use standard sized filter racks with standard sized filters everywhere possible. This will allow you to reduce air filter inventories and will allow you to easily change filter types in the future. Standard size filters are generally cheaper and easier to purchase.

When it comes to specific filters, we recommend using 95% ASHRAE (MERV 14) final filters where ever possible. Otherwise, you will be calling us for duct cleaning in a few years.

Now for drain pans. We suggest using stainless steel. It’s also important to make sure that the pans drain properly. Commonly used drain tablets erode galvanized drain pans. (Note: we do not recommend using chemical tablets for your drain pans. When they dry out, they send dry chemicals into your critical air streams).

You’ll want to also specify external insulation on your ductwork, wherever possible. Internal insulation collects contaminant and is difficult to clean. The insulation deteriorates over time, releasing into the air stream, causing indoor air quality problems. Internally lined ductwork is much more likely to harbor fungal and bacterial growth in the event of moisture problems.

In terms of ductwork, we suggest only using flex type ductwork where you have to. One foot of flex duct equals about ten feet of hard duct in terms of resistance to air flow. Flex duct runs over five feet long waste energy and are likely to be collapsed, kinked or blown out, greatly reducing air flow.

Fans and motors need to be located upstream of filtration. Fans and motors create particulate contamination that need to be filtered out of air stream. This is particularly important for areas in facilities that need high levels of cleanliness.

Installation

Proper installation will ensure maximum functionality for your air filtration system.

Install enough access doors in the mechanical room HVAC ductwork to be able to inspect and to enter the ductwork. Additionally, install an access door at each fire damper and make sure piping and other obstructions are not installed in front of the access doors.

Additionally, stagger air filters frames in a W type arrangement instead of having them in one plane. This gives you much more filter service area.

Put pre-filters in a separate frame than the final filters, leaving a space between the frames. This allows you to install a separate differential pressure gage for each filter bank.

Lastly, we suggest installing differential pressure gages across each filter bank and change filters on differential pressure instead of visual appearance or a given time frequency.

By considering these three factors, you are ensuring the best indoor air quality possible for your healthcare facility. Don’t hesitate to reach out to our team at Carolina IAQ for evaluation and guidance as you plan construction for your facility.

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