St. Louis insulation & air sealing

The cheapest heat is the heat you already paid for.

St. Louis runs 4,433 heating degree days and 1,713 cooling degree days a year, and most houses here are losing a good share of both straight through the ceiling. Arch City Insulation seals and insulates attics, crawl spaces, rim joists and walls across the whole metro — measured before, measured after, photographed throughout.

No cost, no obligation, and you keep the report and the photos either way.

R49What DOE recommends for a St. Louis attic that already has a few inches
84.9Nights a year at or below freezing, Lambert 1991–2020 normals
45Metro cities and jurisdictions covered
Why homeowners call us

We measure the R-value you actually have before quoting anything, and we hand you the number in writing.

The St. Louis problem

It is not the cold. It is the cycling.

NOAA's 1991–2020 normals for Lambert put 84.9 nights a year at or below freezing, but only 19.3 days that never climb back above it. Most St. Louis freezes thaw the same day.

That daily swing is what makes an under-insulated, under-sealed attic here different from one in Minnesota. Warm wet air pushes up through the ceiling all night, hits cold sheathing, condenses, and then everything warms up and dries just enough that nobody ever sees it — until the plywood is dark and the batts are matted flat. And in a zone 4A summer, the same missing insulation runs the other way through 1,713 cooling degree days.

Have someone look at it

Air first, then insulation

Blowing more fibre over a leaky ceiling plane buries the problem instead of fixing it. Sealing comes first, every time, and it is the cheaper half.

Measured, not eyeballed

We tell you the R-value you have before we tell you the one you need, and we mark the finished depth on a ruler at the hatch so you can check it yourself.

The rebate is part of the quote

Which programme applies here depends on which side of the river you are on. We work that out before you sign, not after.

Free home energy assessment

It starts with the attic hatch.

Somebody comes out, gets in the attic and under the floor, measures what is there and finds where the air is going. Takes about an hour, and you get the report whether or not you hire us.

STEP 01

Tell us the address

We look up the house, the vintage and the code that applies in your jurisdiction before anyone knocks on the door.

STEP 02

We measure what is there

Depth, material, condition, and the ceiling plane underneath it. Infrared where the picture needs it.

STEP 03

You get numbers, not a pitch

Current R-value, target R-value, the cost, and which rebate programme your address actually qualifies for.

Start my free assessment
What we do

Insulation and air sealing. That is the whole list.

We are not a remodeler that also blows attics. Every crew and every truck here points at one thing — across greater St. Louis, from the city out to Franklin County and across the river into the Metro East.

Attic insulation

The one that pays for itself first. We measure what is up there, air seal the ceiling plane underneath it, then blow to a depth we mark on a ruler you can see from the hatch.

  • Blown fibreglass and cellulose
  • Depth marked and photographed
  • Baffles at every soffit bay
  • Hatch and pull-down stairs sealed

Air sealing

Insulation slows heat. It does not stop air. Sealing the top plates, chases and penetrations before insulating is the difference between a warm house and a deep pile of fibre.

  • Top plates and wire penetrations
  • Chases, soffits and dropped ceilings
  • Rim joist and sill plate
  • Blower door before and after

Crawl space & rim joist

The coldest floor in a St. Louis house is usually over a vented crawl space. We fix the rim joist first, because that is where the air is actually moving.

  • Closed-cell foam at the rim
  • Encapsulation and vapour barrier
  • Sub-floor batt replacement
  • Vent and moisture assessment

Wall insulation

Pre-war St. Louis brick and frame houses were built with nothing in the walls. Dense-pack goes in through small holes and comes back out as a wall that does not radiate cold.

  • Dense-pack cellulose
  • Injection foam where it suits
  • Interior or exterior access
  • Thermal imaging to verify fill

Insulation removal

Rodent-contaminated, water-damaged or simply exhausted. It comes out under negative pressure into sealed bags, and the deck gets treated before anything new goes down.

  • Vacuum removal, sealed bagging
  • Rodent contamination
  • Fire and water damage
  • Vermiculite referred out, not disturbed

Home energy assessment

Before anything is quoted: what R-value you actually have, where the air is going, and what the fix is worth. A written report with photographs, yours whether you hire us or not.

  • Measured attic R-value
  • Infrared scan of the ceiling plane
  • Written scope with priorities
  • Rebate eligibility checked
Rebates

The same attic is worth more in Illinois.

This is the strangest thing about insulating a house in this metro, and almost nobody tells you. Two houses of the same age, twenty minutes apart, get completely different money for exactly the same work — because one is an Ameren Missouri customer and the other is an Ameren Illinois customer, and the two states regulate efficiency programmes differently.

We check which one applies to your address before quoting, and we tell you what the programme requires — because both of them require the contractor to be enrolled, and a contractor who is not cannot get you the money no matter what they promise.

Read the full rebate guide

Illinois side — Ameren Illinois

$1.10 per square foot

attic insulation on Ameren Illinois' 2026 discount table. Wall insulation the same, $2.00 per linear foot rim joist, $0.70 per cubic foot per minute (CFM) of air leakage reduced for air sealing — and that last one has to be pre-approved before the work starts. Applied by a registered Program Ally, not mailed to you.

Missouri side — Ameren Missouri

$0.20 per square foot

ceiling and attic insulation inside the Pay As You Save programme, the 2026 programme year — but only where the attic starts at R-20 or below and reaches R-38. Recovered through a monthly charge on the bill rather than paid up front, and that charge cannot exceed 80% of the estimated saving. Income-eligible households can get attic insulation at no charge through CommunitySavers instead.

Federal 25C

Ended 31 Dec 2025

The 30% Energy Efficient Home Improvement Credit is not available for work placed in service in 2026. Anyone still quoting it as part of your price is quoting something that no longer exists.

How we work

Straightforward, and mostly out of your way.

Four steps, and you know what is happening at each one. No surprise change orders, no crew that opens up a crawl space and disappears for a week.

01

The assessment

We get in the attic and the crawl space, measure what is really there, run the infrared, and send you the whole set of photographs — yours to keep, hire us or not.

02

The scope and the price

One line-itemed proposal: what gets sealed, what gets insulated, the R-value we are building to, and which rebate you qualify for. One number, and it is the number.

03

The install

Floors and stairs protected, hoses run on drop cloths, and the depth marked on a ruler at the hatch so you can check the job yourself from the ladder.

04

After we leave

A blower-door number before and after where the job called for one, the rebate paperwork filed for you, and photographs of the finished depth.

Credentials

Registered where the city requires it, enrolled where the rebate requires it.

Neither Missouri nor Illinois licenses insulation contractors at state level. What does exist is municipal contractor registration — a good number of metro cities require it before a permit is pulled — and utility programme enrolment, which is what decides whether your rebate is real.

Where we work

The whole metro, both sides of the river.

Every city below has its own page with the energy code that jurisdiction actually enforces, the R-value it requires, whether an attic job needs a permit there, and the building department's own number. In Missouri those change from one side of a street to the other.

See every city we cover

Find out what your attic is actually costing you

Free assessment, a measured R-value, and photos you keep either way.

Free assessment