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HVAC Services · New Construction

New Construction & Remodel HVAC Design

Builders, GCs, and homeowners trust M&M for full-design HVAC on new homes, additions, and major remodels. Manual J load calcs, Manual D duct design, and clean rough-ins on schedule.

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Family-owned since 1992 Licensed & insured All makes and models Free estimates

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Same-day service available across the St. George metro area. Free estimates on installs.

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Designed, not guessed

The HVAC system on a new home should outperform code, not just pass inspection.

Most callbacks on a new home come from undersized returns, leaky duct joints, or an oversized AC that short-cycles. We don't cut corners on rough-ins. Our designs are calculated, not guessed, and our installs pass inspection the first time.

The vast majority of comfort complaints in newer Southern Utah homes trace back to three things: oversized cooling that short-cycles and never pulls humidity, undersized returns that starve the blower and create static-pressure issues, and leaky duct joints in unconditioned attic space that lose 20–30% of conditioned air before it reaches the registers. None of these are mistakes that show up at the final inspection. They're problems the homeowner discovers in their second summer, by which point the warranty conversation is awkward.

We design around the worst-case load, which in our climate is summer cooling on a 110° afternoon, using Manual J load calcs and Manual D duct designs. Our installs hit blower static pressure targets, supply air temperatures, and zone balance numbers we can verify with manometer and probe. The result is HVAC that performs, builders who don't get callback calls, and homeowners who don't have to discover problems on their own. Read more on proper AC sizing.

Request a project bid T.I. or commercial?

Our design process

Six checkpoints that prevent callbacks.

Engineering on the front end is the cheapest place to spend money on any project.

Manual J

Residential load calculation

Window-by-window, room-by-room cooling and heating loads using ACCA-approved methodology and our specific climate inputs.

Manual S

Equipment selection

Match equipment capacity to actual loads at design conditions. No 'round up to the next size' default.

Manual D

Duct design

Trunk and branch sizing, register selection, total external static pressure check before drywall.

Rough-in coordination

Coordination with other trades

Chases, soffits, equipment closets, gas line routes, all sequenced with framing, plumbing, and electrical.

Pre-drywall walk

Before insulation

Final review of duct sealing, return paths, and equipment access while everything is still visible.

Commissioning

Performance verification

Static pressure, supply air temps, refrigerant charge, and zone balance verified at trim-out.

Why builders & homeowners choose us

An HVAC trade that hits its dates.

Schedule reliability, clean rough-ins, and inspections that pass the first time.

Family-owned since 1992

Three decades of new construction across Washington County. Builders we worked with in '95 still call us.

Licensed & insured

Utah HVAC, gas, and refrigeration licenses. All work permitted and inspected.

On-time, on-spec

We hit our rough-in dates. We don't move trim crews onto your job before drywall is finished.

In-house fabrication

Sheet metal shop on-site. Custom plenums, transitions, and chases on schedule.

Service area

New construction & remodels across Southern Utah

We work with builders and homeowners on production neighborhoods, custom builds, additions, and remodels in every city across the metro.

Washington

0 minutes. Our shop is in Washington

St. George

8–15 minutes from our Washington shop

Hurricane

20–25 minutes from our Washington shop

Ivins

20 minutes from our Washington shop

Santa Clara

15 minutes from our Washington shop

La Verkin

25 minutes from our Washington shop

Toquerville

25 minutes from our Washington shop

Springdale

45 minutes from our Washington shop

What working with us looks like

From plan review to trim-out.

A four-step process that fits cleanly into your construction schedule.

  1. 01

    Plan review & bid

    We review architectural plans, run load calcs, and quote design + install, line-itemed and clear.

  2. 02

    On-site assessment

    Walk the lot or jobsite, coordinate with framers and electrical, identify any chases or routing issues early.

  3. 03

    Honest schedule

    Rough-in date locked in based on your build schedule. We tell you what we need and we hit our windows.

  4. 04

    Quality install & commission

    Performance verified, inspections passed, owner walkthrough complete. We stand behind the work.

New construction HVAC FAQ

Do you do Manual J load calculations on every new construction project?
Yes. Every new home and addition we touch starts with a Manual J residential load calculation that accounts for window orientation, glazing, insulation, infiltration, and our specific desert climate inputs. We don't size by square foot. Building inspectors increasingly ask for the J calc on permit submittal, and getting it right at design avoids the most common callback in new construction: oversized AC that short-cycles.
Do you work directly with builders and GCs?
Yes. We have long-running relationships with several builders across Washington County and welcome new ones. We bid clean, hit our rough-in schedules, coordinate with framers and electricians, and clean up after ourselves. Our trim-out crews don't show up before drywall is finished, and our work passes inspection without callbacks more reliably than any HVAC trade in the area we know of.
Can you handle additions and remodels, not just new builds?
Definitely. Additions are some of the most rewarding projects we do because they require real engineering. Extending a duct trunk that was never designed for additional load almost never works without modification. We assess the existing system's capacity, redesign as needed, and integrate the addition cleanly so the homeowner doesn't end up with hot or cold rooms after the project.
What is Manual D and why does it matter?
Manual D is the duct-design counterpart to Manual J load calcs. It calculates trunk and branch sizes, register selection, and total external static pressure so the system actually delivers the airflow the equipment is rated for. Most HVAC callbacks in new construction trace back to undersized returns or excessive duct restriction, and Manual D is how you avoid that. We do it on every job.
How early in the process should we bring you in?
As early as possible. Ideally during plan review, before mechanical chases are finalized and before the foundation is poured. Catching things like a missing return chase, a too-tight equipment closet, or insufficient soffit space at design is essentially free; catching them after framing requires re-work. Even on smaller projects, a 30-minute call before plans are stamped pays for itself.
Do you handle high-end custom homes with complex zoning?
Yes. We do a fair amount of work on Kayenta-area, Stone Cliff, Entrada, and Ledges-area custom builds: multi-zone systems with smart thermostats, hidden returns, integrated humidification, and tucked-away air handlers in tight closets. These projects reward thoughtful design and clean execution, and they're exactly the kind of work we built our shop around.

Bringing us in early on a project saves money.

Plan review, design coordination, and a bid that holds up through framing. Call the shop or send us your plans.

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