Greater Lansing
Crawl space encapsulation & insulation
The air in your crawl space ends up in your living room, which is the real reason to do this and not the cold floor that prompts the call. Here is what encapsulation actually involves, why plastic on the dirt is half a job, and the one question that has to be answered before any of it.
What is actually wrong
The air in your crawl space ends up in your living room. Warm air rises and leaves through the top of a house, and the replacement is drawn in from the bottom, so a damp crawl space with mold on the joists is not a sealed-off problem under the floor — it is the supply end of the air in the rooms above it. That, rather than the floor being cold, is the real argument for doing this work, although the cold floor is usually what prompts the call.
Encapsulation is not a sheet of plastic on the dirt, and this is where most of what gets sold under the name falls down. Michigan’s code for a closed crawl space asks for three things, not one. A continuous Class I vapor retarder over all exposed earth, with the joints lapped six inches and sealed or taped, carried at least six inches up the stem wall and attached and sealed to the wall or the insulation. Then air exchange — either continuously operated mechanical exhaust at one cubic foot per minute for every fifty square feet of floor, with an air path to the rest of the house, or a conditioned air supply at the same rate with a return path. And the perimeter walls insulated to the energy code. Plastic down with no air exchange is the half of the job that traps moisture.
The question that comes before all of it, and the one that can stop the job: what is down there and how does it vent. The code is blunt — a combustion water heater in a conditioned crawl space has to be power vented or direct vented, and an unvented combustion space heater is not permitted at all. Closing up a crawl space with a natural-draft furnace or water heater in it is a code problem and a carbon monoxide problem in the same breath, and it is not fixed by being careful. It is fixed by the appliance being addressed first.
And the order of work, which is the same order as everywhere else on this site: the water comes first. Encapsulating a crawl space that takes standing water after heavy rain is sealing the water in with the house. Gutters, downspouts, grade and a sump where one is genuinely needed all come before a membrane goes down.
The part worth knowing about the money: crawl space insulation, rim joist insulation and floor insulation are all on the Consumers Energy rebate measure list, and that program has no income test at all. Rim joist air sealing in particular has one of the best ratios of cost to energy saved of anything in a house, which is exactly why it is on the list. The rebate has to be reserved after a diagnostic assessment rather than before, so the order matters there too.
Where this stops
When it is not a handyman job
This is at the top of the page rather than the bottom because getting it wrong costs you a wasted visit. Insured, and no contractor license is claimed or implied — the Michigan residential builder license is not held.
- If there is a natural-draft furnace or water heater in the crawl space, the appliance is addressed by a licensed mechanical contractor before anything gets closed up. The code requires a combustion water heater in a conditioned crawl space to be power vented or direct vented and permits no unvented combustion space heater at all, and the reason behind the code is carbon monoxide. This is the one boundary on the page that is not about scope.
- No mechanical work. Installing the continuous exhaust fan, or tying a conditioned supply and return into the existing duct system, is a licensed mechanical contractor’s line — named on the quote and coordinated rather than absorbed.
- No structural work. Sagging joists, a rotted sill plate, a failing pier or a cracked foundation wall is assessed, reported and referred, and in the case of anything load-bearing that is a structural engineer first.
- Mold: inspection and surface treatment only, with remediation past small areas referred to a certified specialist. The same line as everywhere else on this site, because it is this company’s own invoice wording — and a mold-covered crawl space is common enough that it is worth saying here.
- Radon: the membrane is ours, the fan and the system design are a certified mitigator’s. Sub-membrane depressurization is the recognized technique for a crawl space and the membrane is only one half of it.
- Standing water is solved before it is covered, never instead. If the honest answer is that the drainage has to be fixed first and the membrane waits, that is what gets said.
- No excavation, no lowering a crawl space floor and no underpinning. This company holds no residential builder license, which is said here rather than discovered later.
- A closed crawl space is a code-governed assembly and some of this work needs a permit and an inspection. Where it does, that is established before the quote rather than after the work.
- In a house built before about the mid-eighties, old pipe lagging and duct wrap get sampled before they are disturbed rather than pulled out and bagged on the day.
The work itself
What actually gets done
Clear it out first — fallen insulation, old torn vapor barrier, construction debris and whatever else forty years has left down there.
Deal with the water before the membrane: downspouts, grade, and a sump where the crawl space genuinely takes water.
A continuous sealed membrane over all exposed earth, joints lapped and taped, carried up the stem wall and sealed to it — to the code specification rather than to whatever is quickest.
Seal the vents where the design is a closed crawl space, and build in the air path the code requires rather than leaving it sealed and stagnant.
Insulate the stem walls, and insulate and air seal the rim joist, which is where the best energy return in the whole assembly is.
Pest exclusion while it is open: the sill gaps, the pipe and wire penetrations, the places a mouse has been using as a front door.
An access hatch or door that actually seals, because the best membrane in the county does nothing with an open hatch above it.
Sub-membrane pipe rough-in where a certified radon mitigator is coming, so their fan has something to connect to.
Photograph the whole thing and hand it over. Most homeowners have never seen their own crawl space, and the before-and-after is the only way this work is ever visible.
This work sits inside General Repairs, which carries the invoiced price bands for the trade with the sample size printed beside every figure.
What it costs
There is no price list for this, and here is what actually decides the number.
The same three words describe a twenty-minute job and a two-day one. Rather than publish a figure that is wrong for one of them, here is what moves it — so you can work out roughly which end of it you are at before anybody comes out.
Area and headroom. A crawl space you can kneel in and one you can only lie in are different jobs at the same square footage.
What has to come out before anything goes in, and how far it has to be dragged to get out of the access hatch.
Whether there is water, and what fixing that turns out to involve.
How much insulation is going in, and whether the rim joist is reachable all the way round.
Whether the vents are being closed, which brings the air-exchange requirement with it.
Whether a licensed mechanical contractor has to be involved for the appliances or the air supply, which is priced and arranged separately rather than absorbed.
Access. A hatch in the back of a closet changes the labor on every single item above.
Whether anything down there needs sampling before it is disturbed — old pipe or duct wrap in a pre-1980s house.
How to get a real number
Somebody comes out, looks at it properly, and you get a fixed price in writing with the work set out line by line and the exclusions written down as plainly as the inclusions. Coming out to do that is not charged for, and neither is working out what is wrong. If something is found once a wall or a floor is open, it is priced as a written change order and you decide before the work carries on rather than after it is billed. Materials are supplied at cost with the receipt attached, first-time customers get 10% off labor, and labor carries a one-year craftsmanship warranty.
If this is happening right now
What to do in the next five minutes, and what happens when you ring.
Before anybody arrives
- Go and look, or get somebody to photograph it for you. Standing water, a torn barrier, insulation hanging out of the joists and black staining on the subfloor are all things you can see from the hatch with a flashlight.
- Find out what appliances are down there and how they vent, because that single answer decides whether this job can be done at all in its usual form.
- Note whether it smells. A crawl space you can smell in the house is already telling you where the air in your rooms is coming from.
- Check the vents. If they are open, that is the current design; if somebody has stuffed them with insulation, that is a closed crawl space without any of the rest of the work, which is the worst of both.
- Follow the downspouts and look at the grade, same as for a basement. Water outside is the cause of nearly everything inside.
- If there is loose fallen insulation lying on the ground, leave it. It is holding whatever has grown on it, and dragging it out without a bag is how that gets into the house.
- Do not seal a crawl space up yourself for the winter. Closing the vents without the air exchange and the membrane is the combination that grows mold on the joists.
Call the business line
(517) 505-7135Answered Monday to Friday, 08:00 to 18:00. There is no out-of-hours line and this page is not going to invent one — outside those hours, leave a message with the address and what is happening, and it is picked up in the morning.
On the call you get asked what is happening, what else in the building is affected, and whether it is still getting worse. That is how it gets decided whether this is our job at all — and if it is not, you get told that on the phone rather than after somebody has driven out.
- No trip charge
- No call-out fee or minimum
- No diagnostic fee
- No charge for a return visit
True across all 84 written quotes this company has issued. Most contractors in this market charge to turn up.
Or send the detailsWhen the right answer is not this company
- You can smell gas
- Leave the building and call the utility from outside. Not us, and not later.
- Water you cannot stop
- Your main shut-off first, then a licensed plumber. Every minute of this one costs money.
- Sewage backing up, or several fixtures at once
- A licensed plumber with a camera. That is the shared line, not a fixture, and a cable down one sink will not touch it.
- Sparking, scorching or a burning smell at an outlet or a panel
- Breaker off, and a licensed electrician. Electrical work here is repair and like-for-like replacement, and this is neither.
- No heat, or heating and cooling equipment that has failed
- A licensed mechanical contractor. That trade is not offered here at all, and knowing that in one phone call is worth more than a visit.
Questions people actually ask
What is crawl space encapsulation, really?
Three things rather than one, which is where most of what gets sold under the name falls short. Michigan’s code for a closed crawl space asks for a continuous Class I vapor retarder over all exposed earth, with joints lapped six inches and taped and the edges carried at least six inches up the stem wall and sealed to it. Then air exchange: either continuously operated mechanical exhaust at one cubic foot per minute for every fifty square feet of floor with an air path to the house, or a conditioned supply at the same rate with a return path. And the perimeter walls insulated to the energy code. A sheet of plastic laid on the dirt with no air exchange is the half of the job that traps moisture rather than removing it.
Is it safe to close up a crawl space that has a furnace or water heater in it?
Not without dealing with the appliance first, and this is the one thing on this page that is a safety matter rather than a question of scope. The code requires a combustion water heater in a conditioned crawl space to be power vented or direct vented, and it does not permit an unvented combustion space heater at all. The reason is carbon monoxide: closing up the space the appliance draws its combustion air from, and changing the pressure around its flue, can bring exhaust gases back into the house. So the first question on any crawl space visit is what is down there and how it vents, and the answer sometimes stops the job until a licensed mechanical contractor has been.
Should I insulate the floor above the crawl space or the crawl space walls?
If the crawl space is being closed and encapsulated, the insulation goes on the perimeter stem walls and the rim joist, and the floor above is left alone — the crawl space becomes part of the house rather than part of the outdoors. If it stays vented, insulating the floor above is the right answer, and batts stapled up into the joists that are now hanging down and holding moisture are worse than nothing. Which of those two designs you have should be a decision, and in most houses we look at it has become an accident.
Will encapsulating my crawl space fix a cold floor and a musty smell?
Usually both, and the smell is the better reason. Warm air leaves the top of a house and the replacement is drawn in at the bottom, so the air in a damp crawl space ends up in the rooms above it — a crawl space you can smell in the living room is telling you exactly that. The cold floor is what prompts the call and the air quality is what makes it worth the money. What it will not fix on its own is water: if the crawl space takes standing water after heavy rain, the drainage comes first, because a membrane over that is sealing water in with the house.
Is crawl space insulation covered by a rebate?
Crawl space insulation, rim joist insulation and floor insulation are all on the Consumers Energy measure list, and that program has no income test — the eligibility check is whether Consumers sends you a gas or electric bill. Rim joist air sealing in particular is on the list because it has one of the best ratios of cost to energy saved of anything in a house. One rule matters: the rebate has to be reserved after a full diagnostic assessment, not before the work, so the order of operations decides whether the money is available at all. The energy rebates page on this site sets out all four programs.
There is mold on the joists in my crawl space. Can you deal with that?
Up to a point, and the line is the same one printed on this company’s own invoices: inspection and surface treatment only, with remediation past small areas referred to a certified specialist. Framing is a hard surface and it cleans and treats; fallen insulation and anything porous comes out and gets bagged. But a crawl space with growth across the whole underside of a floor is a remediator’s job, not a handyman’s. And it will come back regardless unless the moisture is fixed, which is the actual point of encapsulating it.
Do you dig out a crawl space to make it taller?
No. Lowering a crawl space floor means excavation and usually underpinning, which is heavy equipment and a licensed residential builder’s work, and this company holds no such license. What is done here is everything inside the space as it stands — clearing it, dealing with the water, the membrane, the stem walls, the rim joist, pest exclusion and a hatch that seals.
What does crawl space encapsulation cost?
There is no rate card, and headroom changes it more than area does — a space you can kneel in and one you can only lie in are different jobs at the same square footage. It is set by what has to come out first and how far it has to be dragged, whether there is water and what fixing it involves, how much insulation is going in, whether the vents are being closed and the air exchange that brings with it, whether a licensed mechanical contractor is needed for the appliances, and how bad the access is. Somebody comes out, goes down there, and puts a fixed price in writing with photographs. Coming out is free.
Book a crawl space survey
Tell us two things when you get in touch: whether it ever has standing water, and whether there is a furnace or water heater down there and how it vents. Those two answers shape the whole job. Somebody goes down there, photographs all of it, and puts a fixed price in writing — and you get the photographs either way, because most people have never seen their own crawl space. Coming out is free.