Moving into a new apartment is supposed to feel like a fresh start, not the start of constant sneezing, congestion, and irritation. But for one renter, a dirty HVAC return and a weak filter may be turning their new home into a source of allergy flare-ups.

What's happening?

On Reddit, the renter explained that they and their fiancé had moved into the apartment the month before and had since noticed their dust and dander allergies worsening as they examined the HVAC setup more closely.

According to the post, the apartment has a Lennox Merit Series system, with the filter located in a wall return register. The renter said they vacuum both the register and the filter every week, but described the filter as "a very open-knit kind of filter" that seems to catch only larger debris, such as dog hair.

The area that appears to be causing the most concern is beneath the furnace, which the poster said sits atop a hollow box. Inside that dirty-looking space, they reported finding drywall debris, wood screws, exposed insulation fibers, dust, and splintered pieces of engineered wood board.

They wanted to know if switching to a different return filter would be possible without restricting airflow or "putting more stress on the unit and motor."

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Another option is Merino, which offers single-room, ultra-efficient HVAC systems at a lower price point. 

Why does it matter?

Indoor air quality can have a major effect on daily life, particularly for people living with severe allergies or asthma. Dust, insulation fibers, pet dander, and construction debris inside returns or nearby cavities can all add to that burden if they are repeatedly disturbed or pulled into circulation.

The post also highlights a common issue for renters: limited control over HVAC systems. While many tenants can replace or clean a filter, they may not be able to seal leaky returns, remove hidden debris, or upgrade equipment without a landlord's approval.

HVAC systems that do not perform well can leave homes less comfortable and less efficient, potentially driving up energy bills while still doing a poorer job of filtering indoor air. Cleaner, more efficient electric heating and cooling systems can improve comfort while reducing wasted energy at home.

What can I do?

Documenting the issue and sending photos to a landlord or property manager can help establish what is happening. Useful questions include whether the return cavity can be professionally cleaned, whether the proper filter type is installed, and whether the system manual allows for a higher-efficiency filter.

Upgrading filters also requires care. A denser filter is not automatically better if the system is not rated for it, so checking the HVAC model specifications or asking a licensed technician before making a change can help. Portable air purifiers and more frequent dusting may also help reduce exposure in the meantime.

Homeowners looking to lower bills even further can also compare solar quotes through EnergySage. And for those considering an HVAC upgrade, EnergySage's Heat Pump Marketplace is a great place to look or direct willing landlords. 

The renter described the box under the furnace as "pretty gross," and said the issue went beyond basic discomfort: Their allergies were "severe enough that I've tried going through immunotherapy and failed it."

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