How long should I wait after changing the filter before my AC starts cooling again?

Give the system 20–30 minutes after changing a severely clogged filter. If the evaporator coil froze due to restricted airflow, you may need to let it thaw for 2–4 hours with the system in fan-only mode before full cooling returns.

My AC runs constantly but can't reach the thermostat setpoint on hot days. Is that normal in Fairfax?

On extreme heat days, it's normal for a correctly sized AC to run nearly continuously. If it's running non-stop on a moderate summer day and still can't catch up, you likely have an airflow problem, a refrigerant issue, or a system sizing problem.

Should I turn my AC off if it's not cooling, or keep running it?

If you suspect a frozen coil, switch to fan-only mode or turn the system off. For other issues like a dirty filter or dirty condenser, you can continue running while you address the fix. When uncertain, fan-only is the safest setting.

How do I verify an HVAC contractor is licensed in Virginia?

Virginia requires all HVAC contractors to hold an active license through the Virginia Department of Professional and Occupational Regulation (DPOR). You can verify any contractor's license status on their website.

Is a heat pump a good replacement for a failing AC in Northern Virginia?

Yes — modern variable-speed heat pumps are well-suited to NoVA's Climate Zone 4A. They qualify for the largest federal tax credits available in 2026 and Dominion Energy offers rebates for qualifying installations.

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Planning a Whole-Home Renovation? The HVAC Decisions to Make Before Work Begins

In a whole-home renovation, HVAC must be coordinated with electrical, insulation, and the construction schedule. The decisions to make before work begins, the full timeline from design through commissioning, and why commissioning matters.

October 13, 2026 By the Fairfax Mechanical Team 10 min read

Short answer: In a whole-home renovation, HVAC decisions must be coordinated early with your electrical upgrades, insulation work, room changes, and construction schedule, and planned around key milestones, ending with proper commissioning. Deciding on system type, sizing, duct layout, and zoning before construction prevents costly rework and ensures the finished home is comfortable and efficient. Fairfax Mechanical is an experienced, licensed Virginia HVAC contractor that coordinates whole-home renovation HVAC from planning through commissioning, so every part of your renovated home is comfortable and efficient.

Planning a whole-home renovation? The HVAC decisions to make before work begins

A whole-home renovation is a major undertaking, and HVAC is one of the systems most easily overlooked until it is too late to plan properly. Because HVAC touches nearly every room and coordinates with electrical, insulation, and construction schedules, the decisions you make before work begins shape your home's comfort for decades.

Why HVAC coordination is critical in a whole-home renovation

A whole-home renovation often changes the very things that determine HVAC needs: layouts, insulation, windows, square footage, and room uses. At the same time, HVAC must be coordinated with electrical capacity, especially if you are adding a heat pump or going all-electric, with insulation and air-sealing work, which changes the load, and with the construction timeline, since ductwork and rough-in must happen before walls close.

Treating HVAC as an afterthought in a project this big leads to compromises, delays, and discomfort.

The HVAC decisions to make before work begins

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A whole-home load calculationReflecting the renovated layout, insulation, and windows.
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System type and whether to replaceFurnace, heat pump, dual-fuel, or zoning, chosen deliberately rather than by default.
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Duct layout redesignedFor the new floor plan, not patched onto the old one.
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ZoningFor comfort across the renovated home.
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Electrical coordinationWith your renovation's electrical upgrades and available capacity.
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Insulation coordinationSince efficiency improvements may reduce the required system size.
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PermitsFor all HVAC and related work.

The whole-home renovation HVAC timeline

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Planning and designLoad calculation, system decisions, duct and zoning design, coordination with the architect, electrician, and insulation plan, and confirming permits.
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DemolitionRemove old equipment and ducts as needed, and assess existing conditions.
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Rough-in, before walls closeInstall ductwork, line sets, venting, and HVAC electrical, coordinated with the other trades' rough-in.
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Pre-drywall inspectionPermit inspection of the mechanical and electrical rough-in.
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Insulation and drywallThe envelope is completed around the planned system.
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Equipment installationSet and connect the new system.
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Commissioning and final inspectionStart up, balance airflow room by room, verify performance, and pass the final inspection.

Why commissioning matters

The final step, commissioning, is where a renovated home's comfort is proven. Balancing airflow to every room, verifying the system performs as designed, and confirming it is correctly charged and controlled is what separates a renovation that looks done from one that is actually comfortable. Do not skip it.

The step most often skipped

A system that is installed but never balanced leaves some rooms hot, some cold, and the homeowner convinced the equipment is the problem when the airflow was never adjusted.

Why choose Fairfax Mechanical

We are an experienced, licensed Virginia HVAC contractor, and we coordinate whole-home renovation HVAC from planning through commissioning, covering sizing, duct design, zoning, and coordination with your electrical and insulation work, so every part of your renovated Northern Virginia home is comfortable and efficient. We serve Fairfax and all of Northern Virginia.

“In a whole-home renovation, HVAC is either planned into the drawings or paid for twice. There is rarely a middle path.”Fairfax Mechanical Technical Team, Fairfax, VA

Planning a whole-home renovation? Coordinate the HVAC early.

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Frequently Asked Questions

When should HVAC be planned in a whole-home renovation?

Before work begins, during design. Layouts, insulation, windows, and room uses are changing, and ductwork and rough-in must happen before walls close, so HVAC needs to be coordinated with the architect, electrician, and insulation plan from the start.

Does a whole-home renovation mean I need a new HVAC system?

Not necessarily, but it is the right time to decide deliberately. A load calculation reflecting the renovated layout, insulation, and windows tells you whether your existing equipment still fits the home you are creating.

Why does insulation coordination matter during a renovation?

Efficiency improvements reduce your home's heating and cooling load, which can mean the correct system size is smaller than before. Coordinating insulation and HVAC planning prevents buying more capacity than the renovated home needs.

What is commissioning and why does it matter?

Commissioning is the final step where the system is started up, airflow is balanced room by room, and performance is verified and the charge confirmed. It is what separates a renovation that looks finished from one that is actually comfortable.

Why choose Fairfax Mechanical for a whole-home renovation?

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