Five questions, and none of them is "how long have you been in business."
Ask what they inspected. Ask whether air sealing is included. Ask for the final R-value in writing, not inches. Ask what happens to the insulation that is already up there. And ask what documentation you get when the job is finished.
Those five separate a real quote from a cheap one, and the rest of this explains why each matters and what a good answer sounds like. They apply whichever surface is being done, whether that is an attic, having your walls done or finishing a basement. And if you have not yet decided whether to do it yourself at all, settle that first, because it changes the conversation.
The One Question Almost Nobody Asks
Here it is, and it is worth more than the other four combined:
"Where is my house actually losing heat, and are you fixing the air leaks before adding more insulation?"
Adding insulation does not fix gaps. A house leaks air around the attic hatch, around plumbing penetrations and wiring, past pot lights, through ductwork and up through the top plates of interior walls. Insulation slows heat moving through material. It does almost nothing about warm air travelling around it.
Which means a contractor can add a great deal of insulation to your attic, hit the depth they quoted, and leave you with a house that is still drafty and still expensive to heat. Nothing they did was wrong exactly. They just solved the second problem and skipped the first.
The right order is diagnose, air seal, then insulate to the correct level. If the answer you get is about inches and nothing else, you have learned something useful about that contractor.
Before They Quote: What Should They Have Looked At
A quote produced without anyone going up into the attic is a guess with a price on it.
Ask these:
- Did you go into the attic, and how long were you up there? Not a look through the hatch with a torch. Into it, far enough to see the eaves and the far corners, which is where problems live.
- Did you measure the existing insulation or estimate it? There is a real difference between a measured depth and an assumption based on the age of the house. You can do a rough version of this yourself by reading your own attic depth before anyone arrives, which also means you will know if a quote describes an attic that is not yours.
- Did you check the ventilation at the eaves? Blocked soffit vents are the most common defect found in attics, and insulating over them makes it permanent.
- Did you look for moisture? Staining on the underside of the roof deck, damp material, a musty smell. Insulating over a moisture problem hides it and makes it worse.
- What is the existing insulation made of? This matters more than it sounds. Vermiculite may contain asbestos and needs testing before anyone disturbs it. A contractor who cannot tell you what is up there has not looked properly.
On the Quote: What Has to Be in Writing
This is where quotes become comparable or stay uncomparable, and it is usually deliberate.
A quote that says "add 14 inches of insulation" with a price, and nothing about what is happening underneath it, is not a scope. It is a number.
Eight things whose absence should make you cautious:
- Air sealing. Included, excluded, or an extra?
- Ventilation and soffit protection. Are baffles going in, and before the insulation?
- Moisture or mould conditions. What did they find, and what are they doing about it?
- The attic hatch. Insulated and weather-stripped, or ignored?
- The condition of the existing insulation. Staying, partly removed, or all coming out?
- The final R-value. A number you can check, not a depth in inches.
- Exactly what material is being installed. Blown-in fibreglass, cellulose, batt, spray foam. These are not interchangeable and they do not cost the same.
- What is explicitly not included. The honest quotes say so.
On the existing insulation specifically: removal is the single largest variable in the price, so when removal is genuinely needed is worth understanding before you compare two quotes where one includes it and one does not. Those are not the same job and the prices should not be read as if they were.
If a contractor cannot clearly explain what they inspected, what problem they are solving, and exactly what is included, that is the answer to your question.
What a Cheap Quote Is Usually Leaving Out
Insulation is one of the trades where the cheapest quote is often genuinely cheaper to deliver, because the corners that get cut are invisible once the job is done.
Skip the air sealing and you save a half day of fiddly work nobody will ever see. Skip the baffles and you save both the material and the awkward crawl to the eaves to fit them. Leave the hatch alone. Do not bother measuring the starting R-value, because then nobody can check the finishing one. Blow the depth in evenly enough at the hatch end, where the homeowner will look.
Every one of those makes the number smaller. None of them makes the job better.
So the low price may simply mean problems are being covered rather than fixed, and you will not find out for two or three winters. Knowing what the numbers usually look like for your size of attic is the best defence, because it tells you when a quote is not just competitive but implausible.
There is a legitimate version of a cheaper quote, and it sounds different. It says: your attic is straightforward, it does not need removal, the ventilation is already fine, so the scope is smaller. That is a reason. "We are cheaper" is not a reason.
After the Crew Leaves: How to Actually Check
This is the part almost nobody publishes, and it is the real problem with buying insulation: once it is in, you cannot see what you paid for. The air sealing is underneath it. The baffles are at the far edges. The depth at the back of the attic is a matter of trust.
So ask for the evidence up front, as part of the job rather than as a favour afterwards.
What to ask to be given:
- Before and after photographs
- The final installed depth, and the R-value it represents
- Confirmation in writing that air sealing was completed
- Photographs showing the soffit vents and baffles are clear
- Confirmation the attic hatch was insulated and weather-stripped where appropriate
Then go and look yourself, or have an independent inspector do it. You are checking for:
- Even coverage, with no thin spots. Heat finds the thin spot, and an attic that averages the right R-value with bare patches performs worse than a consistent lower one.
- Clear vents at the eaves. If the insulation has been pushed out to the edge and sealed the intake vents, moisture builds up over a winter and shows up as condensation, mould on the sheathing, or ice dams along the eaves the following January.
- Wiring that has not been disturbed or buried. Junction boxes have to stay accessible. Burying one is a code problem as well as a practical one for whoever next needs to find it.
- Ducts that actually leave the building. Bathroom and dryer ducts that stop short in the attic discharge warm wet air straight onto the roof framing. This turns up constantly and it grows mould on sheathing faster than anything else on this list.
- No sign that a moisture problem was simply covered over.
A contractor who is comfortable with all of that is telling you something. One who becomes vague about photographs is telling you something too.
The Questions That Matter Less Than People Think
Worth saying, because these come up and they mostly do not help.
"What brand of insulation do you use?" Within a material type, brand differences are small. The material type matters. The depth matters. The installation matters far more than either.
"How many years have you been in business?" Weak on its own. A long-established company can still run a crew that skips baffles. Ask what they inspected instead.
"Can you beat this other quote?" This invites exactly the behaviour you are trying to avoid. A contractor who drops their price without changing the scope was either overcharging before, or is about to remove something from the job and not tell you.
Ask instead: what is in your quote that is not in theirs. That question is harder to answer vaguely, and the answer tells you whether you are comparing a properly scoped attic job against a cheaper one, or two versions of the same work.
The credential questions are still worth asking once, briefly: WSIB registration and liability insurance are both checkable, and they matter if somebody is hurt in your house. They are just not where the difference between quotes lives.