I don't know for sure what you mean by a "sealed" crawlspace but if you have chosen to not vent it then it is considered to be within the "conditioned" part of the building and therefore you would need to insulate the perimeter if you are in a cold climate and to put a serious vapor retarder membrane on the ground.

Here is a link that might be useful: conditioned crawl spaces

It does not sound reasonable at all. Around here, that's about right for a 2,000 sf full basement, assuming no large rocks have to be dealt with.

No, it does not sound right at all!

We have an unvented attic (you can stand up in it). The whole house is insulated and sealed with spray foam, closed cell in walls, open cell under roof deck. Total cost for 3000 sq ft house = $14,000.

That is a ridiculous amount for a ventless, conditioned crawlspace. Our house is listed at over 4K sq/ft but is a cape and very sprawling, so a big footprint AND our cost was NOWHERE near that. As far as doing it as a DIY project, I personally think it would be cake. There is really nothing to it. And, quite frankly, I'm sure that I would have done a better, tidier job than the insulation company that did the work for our contractor. However, it is an important step to the build, and I would want the contractor to bear the responsibility for getting it done and getting it done right. $20K is a major ripoff...for that size house, there is no way that it should run you more than $5K (ours was $3K 2 years ago), including the additional HVAC cost. Also, your building department will not allow you to do this after the fact. It will most likely need to be marked on the plans, and it will be part of the foundation inspection and the final inspection. Our inspectors failed our foundation inspection the first time around because we didn't have vents...even though our plans were very clearly marked that it was to be a ventless conditioned crawl. We are in Central VA.

Dixiedoodle, does your unvented crawl space follow the natural grade? If so, how is the floor or bottom sealed and waterproofed? If the grade is made level, I see how a concrete floor could be added over a membrane. How deep(?) is it? And how do you access it?
You have completed your home and moved in while I'm still dealing with foundation questions!

Well, our build took over 27 months, so don't be too jealous!

Yes, the crawl follows the natural grade...goes from about 18" to 50". The bottom is sealed with a thick mil plastic (we had them use white rather than the black that is more common, so that I could see the creepy crawlies!). The foundation walls were insulated first with DOW styrofoam and were then covered with the same white plastic. All seams are sealed. We have 5 HVAC vents for the crawlspace. It maintains the temperature pretty well, and it definitely helps with the overall energy efficiency of the house. We access it through a crawl space door which is located in the foundation on the rear side of the house.

Thanks for answering my questions, dixiedoodle. I do appreciate your generosity in sharing! I have been unable to find that info anywhere probably because it is so elemetary or because I did not know how to phrase the question.

We have a crawl space on uneven,(sloped), as well. Currently ours is vented with r-19 batts in the joist cavaties. Future plans will be to insulate the framed pony walls, put 2-3 inches of pea gravel over the grade and cover with 6 mil visquine over the gravel and up the stem walls, framed and concrete. I will block the venting in the winter only to somewhat create a conditioned space. Even with r-19 in the joists, a certain amount of heat will keep the plumbing below from freezing, my understanding from others in our area with the same set up that it never gets colder than in the forties on the coldest part of the year. Opening the vents in the summer, the evenings cool way down and the crawl space stays cool even in the hottest part of summer days. What works for you is dependent on your geograhical location and what is succesful in your area concerning temperature, moisture, extremities, etc.

I am so glad to hear that the price I was quoted was not typical. This is something that we really want to do to create a healthier breathing atmosphere in our house. We were seriously afraid that we would have to make a tough decision.

@sierraeast
I think you completely missed the point of this thread and/or didn't even realize what the topic was. These people are talking about sealed and conditioned crawlspaces. Closing off your vents in the winter and opening them in the summer is not even close to what they are talking about. You should consider actually reading the thread...