24/7 EMERGENCY SERVICE  ·  NASSAU & SUFFOLK COUNTY  ·  631-587-0085
Contracting

Window Installation On Long Island

Energy-efficient windows installed properly — flashed, sealed and finished. NJM handles window installation and replacement for Long Island homes across Nassau and Suffolk County.

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Licensed & Insured
Master Plumber
TASK 86/87 Certified
Navien NSS Certified
22+ YEARS ON LONG ISLAND

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PLUMBING · HEATING · COOLING · CONTRACTING

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Contracting

Window Installation & Replacement On Long Island

Windows are sold on the glass and fail on the installation. Efficiency ratings describe the unit sitting in a laboratory; what you actually get depends on whether the opening was prepared square, whether the flashing was lapped so water runs out rather than in, and whether the gap around the frame was insulated and sealed properly. A high-specification window fitted badly performs worse than a mid-range one fitted well.

NJM installs and replaces windows for homes across Nassau and Suffolk County, and on the south shore in particular the water detail matters more than the brochure. We are a licensed general contractor, so where an opening turns out to be rotted or out of square, the framing repair is the same crew rather than a stop in the job.

24/7 Emergency ServiceLicensed & Insured
  • Master PlumberLicensed to pull permits
  • TASK 86/87Certified for gas work
  • Navien NSSFactory-trained on tankless

22+ years on Long Island · Plumbing, heating, cooling, gas and contracting under one roof

What We Do

Window Services

Full-Frame Replacement

Removing the old window back to the opening, which allows the framing to be inspected and the flashing done properly. The right choice where there is any suspicion of rot or water damage.

Insert Replacement

Fitting a new unit into a sound existing frame. Faster and less invasive where the frame is genuinely in good condition — and we will tell you if it is not.

Rot & Framing Repair

Opening a window frequently reveals damage nobody knew about. As a licensed contractor we repair it rather than downing tools.

Energy-Efficient Units

Modern double and triple glazing, with the specification matched to the wall and the exposure rather than to whatever is on offer.

Egress Windows

Bedrooms — including new ones in a dormer or basement conversion — have egress requirements. Worth getting right at design stage.

Flashing & Weatherproofing

The detail that decides whether the wall stays dry. Lapped so water sheds outward, not sealed in a way that traps it.

Whole-House Replacement

Full replacements scheduled so the house is not open longer than it needs to be.

Permits & Inspections

Where the work requires them, handled as part of the job.

Contracting — before you call

Two kinds of visit. You’ll know which before we come.

We don’t charge to quote a job. We do charge to find a problem nobody has identified yet. Which one you need — and what it costs — gets agreed on the phone, so nothing about the cost is a surprise on the doorstep.

Estimate visitNo charge

You already know what you want done

A boiler replaced, a bathroom rebuilt, a gas line run. We come out, look at the job and give you a number.

No obligation
Diagnostic visitQuoted on the call

Something has failed and nobody knows why

A licensed technician and the time to find what has actually gone wrong. One rate across plumbing, heating, cooling and gas, and one number to reach us on — there is no separate line to find at midnight. You get the figure before anyone is dispatched, and after-hours, weekend and holiday work is quoted the same way.

The rate you are told is the rate

You get the number on the phone, before anyone is dispatched, and it is what you are charged when the technician arrives. One rate across all four trades — plumbing, heating, cooling and gas.

What it pays for

A licensed, insured technician carrying the certifications the work needs, and the time to find what has actually failed — not a quick look and a guess.

Watch for the bait and switch

A call-out advertised at almost nothing gets recovered once someone is standing in your basement. Get the number before anyone travels — from us, or from anyone else you call — and hold them to it when they arrive.

Financing on larger jobs

A boiler that fails in January is not a purchase anyone planned. Financing is available on the big-ticket work, so a system replacement does not have to come out of savings in one go.

What it is normally used for

Boiler, furnace and water heater replacement, a full air conditioning system, a whole-house repipe, sewer and water main work, and larger contracting jobs — kitchens, bathrooms, dormers and extensions.

When to bring it up

At the estimate, before anything is scheduled. It is worth asking even if you think you will not need it, because knowing it is there changes what you are willing to consider fixing properly.

What it does not change

The price of the job. The quote is the quote whether you finance it or not — and on a straightforward repair it is usually not worth the paperwork. We will tell you which one you are looking at.

Financing provided throughSynchronyCredit is extended by Synchrony. Subject to credit approval.
Call 631-587-0085Not sure which one you need? Call and describe it — we will tell you before we book anything.
Before You Spend

New Windows Are Rarely The Cheapest Way To Make A House Warmer

We install windows and we would still rather you heard this first, because the industry is not honest about it and the disappointment afterwards is entirely avoidable.

Windows are usually not the biggest hole in a house. Air leaks around the rim joist, at the attic hatch, through recessed lights and around penetrations generally will typically move more heat than the glass does, and sealing them costs a fraction of a window order. Insulation in an under-insulated attic is the same story. If comfort and bills are the goal, those are normally the first money, not the last.

That is a genuinely inconvenient thing for us to say on a page selling window installation. We say it because the alternative is you spending a large sum, feeling a smaller difference than you were promised, and concluding the whole trade oversells — which, on the energy-savings pitch, it frequently does. Nobody can honestly quote you a payback period without knowing what you have now, and any figure offered before somebody has looked at your house is a marketing number rather than a calculation.

So when are new windows the right call? When the frames are rotted or the sashes no longer close and lock, which is a security and a water problem rather than an energy one. When there is condensation between the panes, meaning the seal has failed and the unit is finished. When single glazing is making a room genuinely unusable in winter. When the operation has become a nuisance you live around. And when you are replacing them for how the house looks and feels, which is a perfectly good reason on its own and does not need an energy justification bolted onto it.

Those are real reasons and we will fit them properly. What we will not do is put an energy number on a proposal that we cannot stand behind. Ask us what we would do first in your house and you will sometimes get an answer that is not a window order.

Quick Rules Of Thumb

  • Air sealing and attic insulation usually move more heat per pound spent
  • A payback figure quoted before anyone has seen the house is marketing
  • Rotted frames and sashes that will not lock are a real reason to replace
  • Condensation between the panes means the seal has gone — that unit is done
  • Wanting the house to look and feel better is a good enough reason by itself
  • Ask what we would do first and the answer is sometimes not windows
Talk It Through — 631-587-0085
More Contracting Services

Everything We Handle In Contracting

One licensed team, one number to call, across Nassau and Suffolk County.

Common Questions

Frequently Asked Questions

Honestly, will new windows pay for themselves?

Not usually on energy alone, and anybody giving you a payback figure before they have seen your house is quoting a marketing number rather than a calculation. In most Long Island houses the bigger heat losses are air leakage around the rim joist and at the attic hatch, and an under-insulated attic — both of which cost far less to put right than a window order. That does not make new windows a bad purchase. It makes energy savings the wrong reason to buy them.

So what is a good reason to replace windows?

Frames that are rotted. Sashes that no longer close or lock, which is security and water rather than heat. Condensation between the panes, which means the seal has failed and that unit is finished regardless of what you do. Single glazing making a room unusable in winter. Operation that has become a nuisance you plan around. And wanting the house to look and feel better, which is a perfectly good reason on its own and does not need an energy argument attached to it.

What would you do first in my house?

Ask us and you will get a straight answer, which is sometimes not a window order. If the attic is thin and the rim joist is open, that is cheaper money and a bigger difference, and we would rather tell you that than sell you the larger job and have you feel less than you expected afterwards. If the windows genuinely are the problem, we will say that too and fit them properly — the installation matters more than the brand.

What is the difference between insert and full-frame replacement?

An insert fits a new window into the existing frame, which is faster and less invasive but relies entirely on that frame being sound. Full-frame takes everything back to the rough opening, so the framing can be inspected and the flashing done from scratch. If there is any sign of water damage or rot, full-frame is the honest answer even though it costs more.

Will new windows lower my energy bills?

They help, but people are often disappointed because the biggest losses in an older Long Island house are usually air leakage through the whole envelope rather than the glass alone. If you are replacing windows specifically to fix draughts and cold rooms, it is worth looking at insulation and air sealing at the same time — we do that work too, so we have no reason to oversell you windows.

How important is the installation compared with the window itself?

More important, and it is where most of the difference in real-world performance comes from. A well-specified window in a badly prepared opening will leak air, and eventually water. Flashing that is not lapped correctly channels water into the wall instead of out of it, and that damage is invisible for years.

What if you find rot when you take the old window out?

We repair it. That is one of the practical advantages of using a licensed general contractor rather than a window-only installer — a rotted sill or header does not stop the job while somebody else is found. We will show you what we found and what it takes to put right before proceeding.

Do I need a permit to replace windows?

It depends on the scope and the jurisdiction — like-for-like replacement often does not, while changing an opening size generally does. We check for your Town or Village and handle whatever is needed.

What are egress requirements?

Bedrooms need a window large enough and low enough to escape through in an emergency. It matters most when you are creating a new bedroom — in a dormer, a basement or an addition — where an existing window may not qualify. Worth designing in from the start rather than discovering at inspection.

How long does a window replacement take?

A straightforward replacement is quick. A whole house is scheduled so the property is not open any longer than necessary, and full-frame work takes longer than inserts. We will give you a realistic schedule after seeing the openings.

Are estimates free?

Yes, free and with no obligation. We will want to look at the openings, because whether you need insert or full-frame changes the number materially. Call 631-587-0085, or use the form and we will be in touch within 24 hours.

Service Area

Proudly Serving Long Island and Surrounding Areas.

Based in North Babylon, working across both counties — close enough to get there fast, local enough to know the housing stock and the permit offices.

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  • Long Island
  • Nassau County
  • Suffolk County

Towns We Serve

Proudly serving all of Nassau and Suffolk County, with deep local roots near our North Babylon home base.

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What Long Island Says

Reviews From Homes & Businesses We've Served

5 out of 5 stars

The experience I had with with NJM Mechanical & Contracting was a pleasant one. I had the pleasure of doing business with Neil. The work I had done was a basement entrance to my yard and it came out wonderful. The work performed as well as the communication is 10/10.

Nick UrziaJune 2026
Reviewed on Google

5 out of 5 stars

I couldn't recommend Neil enough! From start to finish him and his team were professional, efficient and experienced. We had a job pulling up rocks and putting top soil down which I know can be a tedious job. We appreciate the work and look forward to working with the team again.

KrisApril 2025
Reviewed on Google

5 out of 5 stars

Bathroom remodel was completed to my complete satisfaction. Family & Friends enjoy experiencing their spa like bathroom grooming. Contractor was personable, professional, friendly, patient and knowledgeable.

Shirley KendallOctober 2024
Reviewed on Google

Read all 87 reviews from Google and Housecall Pro →

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