Insulation of the sub-floor space with vapor barrier film

I have a private house with a low sub-floor space beneath the main floor, and I need a specialist who will perform complete sealing of this space with thick vapor barrier film. The soil under the house has been retaining moisture for several years, and recently a musty smell has been noticeable from ventilation grilles in the floor, condensation appears on air ducts, and traces of surface mold are visible on several joists near the far wall. I want to solve this problem correctly before it develops into something more serious — both for the house structure and for the health of the residents.

In the scope of work I include removal of old debris and loose insulation lying directly on the earth floor, sealing of obvious gaps around foundation ventilation openings and places where pipes pass through, and then laying thick reinforced film over the entire soil area with edges going up onto the foundation walls and support posts, with overlaps and sealed seams. I would like the seams to be sealed with a special compatible tape rather than regular tape, and the perimeter to be mechanically fastened so the film does not sag or pull away over time. If justified by the layout, I am open to discussing a drainage mat or small sump with a pump in the lowest corner — water accumulates there after heavy rains.

I also want the specialist to assess the existing foundation ventilation openings — I have read that with complete sub-floor sealing sometimes it is more correct to close the vents and install a dehumidifier instead of passive ventilation, and I would appreciate an honest recommendation taking into account the local climate, not a one-size-fits-all template answer. Please include in the proposal a plan for long-term moisture monitoring — whether a separate dehumidifier, connection of prepared air from the heating and ventilation system, or simple periodic monitoring with a hygrometer.

Access to the sub-floor space is through a side hatch on the house, height approximately seventy centimeters, so work will be in confined conditions. I am ready to provide photographs of the current condition, approximate area and measurements on request. I am looking for someone with experience in moisture control work in residential homes, who is comfortable working in confined spaces and who can explain the materials and methods used in simple language. Please indicate the expected timeline, thickness and grade of vapor barrier film you plan to use, as well as whether a final inspection or photo report upon completion is included in the standard process. I would be grateful for reviews or examples of similar completed projects.