Stair vent

[Trevor]

We have a 2021Montana 3761 fl. Underneath the middle stair going into the living room there are some vents that cold air can and does come in, and I assume hot air comes in in the summer. Has anyone closed these off? If so how did you do it?

[Daryles]

The vents under the stairs provide a return air path for the furnace. This return air so helps warm your basement and the plumbing there.
The REAL problem is what i call "Air Gaps" that allow cold (winter) hot (summer) air drafts into your rig. The cold air being more of a concern with freezing pipes.
Here's my list so far...

The problem I have with this "four season" camper is all the "air gaps".
Look under your frame. There are lots of holes and gaps. This allows cold (or hot, summer time) air into your underbelly and can freeze your pipes/tanks.
I believe it is best to secure the perimeter to keep the outsidr air out. In the winter, running your furnace, it must have an air return path. This typically goes from the furnace into the cabin then returns through the stair vents to thr furnace. This circulation helps keep the basement warm and pipes from freezing. This doesn’t help the freswater tank or pipe to it. You need to run your tank heater along with the furnace to prevent it from freezing.
Back to Air Gaps...
I used gorilla tape to close off all small openings (hydraulic lines, slide cylinder).
Use aluminum sheeting and cut to fit around the hydraulic jacks with automotive edge trim. Leave the opening around the propane tanks. They must have ventilation. Or use perforated aluminum sheet to keep mice out.
Take down your basement walls, crawl in and close the doors. You will see daylight coming in through all the gaps along the frame.
Look behind your basement wall aft of the convenience center towards your middle jack. Very large opening where the jack comes through. To close this you will need sheet aluminum cut to fit.
Some have sprayed styrofoam on the inside of the J channel skirt to insulate the frame.
There is a panel under the bottom shelf in the pantry. Behind the panel is the water heater. Again you can see daylight coming in around the edges.
Under your kitchen island there is a panel covering your plumbing. Take it out and there is a big Triangle gap in the corner. Cut and fit styrofoam to fill the gap tight. Use gorilla tape to seal it in place.
Under the bathroom sink you will also find air gaps where the plumbing goes through the floor.
Remove the drawers closest to the fridge. At the back where the propane and electric wiring come through to the oven, there is a gap in the wall by the fridge. Remember the back of the fridge is vented to the outside. Cold air comes in through this gap. Mine is an RV fridge so I have to be careful because on the other side of that wall is the chimney for the fridge heater. I have to use flame retardant insulation here.
Look up in your hitch pin box, you will see your bedroom closet floor and a hole where your 7 way cable goes through the frame. I taped up the hole and wedged 2" styrofoam board up against the floor.
Look at the inside door frame of the pantry. You will see a gap. This leads to the basement.
Make sure your inside and outside slide seals are good.
Look at bottom corners of your windows, you will see 1/4" inch gap for condensation weep hole. Nothing you can do about that unless you want to tape plastic sheets over the windows. If you do, use heavy gauge clear vinyl on the outside. Use metal foil air conditioner tape to secure it to the outside of your rig (doesn't leave residue when removing). Then put either large bubble wrap on the inside of the glass (allows sunlight in) or use clear vinyl again and painters Yellow Frog tape (doesn't leave residue when removing) Having two sealed air voids will help prevent condensation.
Many full time winter campers do this.
Skirting is a must in winter.
Start early on the outside, tape doesnt stick well in freezing temperatures.

I have closed the gaps under the J channel around the jacks. I'm going to fill in the remaining gap with expanding foam. Picture looking up at the jacks from the ground.

[DutchmenSport]

If not using your furnace you can close them off. But that vent is the return vent for your furnace. Close it off and you won't have furnace circulation inside the coach area.

I think the cold air is a problem for almost everyone. I took care of mine by taking a different route.

I removed everything in the front pass through compartment. I removed the back wall and looked inside that gigantic cavity under the coach floor. I noticed all the holes and gaps where the Coloplast is screwed to the frame. I noticed all the holes and gaps where the walls connected and where all the wires passed through from one area to the other and the pipes, air vents and everything.

I used about 20 tubes of calking, about 5 cans of Foamy Stuff (expanding foam for insulation) and a whole bunch of screws and closed up the underbelly, all those holes, and every where I could see light coming through inside that cavity.

The end result was, .... no more cold air comes through that vent.

Your furnace needs to blow under the floor. It's designed to do that. The recirculation is actually under the floor. The recirculation of the air pulls from both the underbelly and the inside of the coach through that vent. But, when the furnace is running, it's now pulling all that air through all those holes, pulling in cold air. The end result is, your furnace has to work harder, use more propane to heat the air being pulled in from all those holes and gaps.

After I did the hole, seal-up project, my furnace works a lot, lot better. I have no cold drafts across the kitchen floor (kitchen is in the bottom middle area), and even the air conditioner doesn't have to run as much as it's not pulling in warm air from outside through those same holes.

The warmth of the camper (in winter) and the cooling of the camper (in summer) improved greatly, actually tremendously. Since I plugged all those holes, there has been no need to close off that vent. Air does not come through it any more if the furnace is not running. And it's sealed now, so the air conditioner is not pulling air from their either.

Take the time to plug all those holes and your heat and AC, and all those drafts on the floor will be much more improved.

[Trevor]

Thanks for all the great info. I’ll get started on all this asap. All this sounds like common sense I just never had given it much thought. Thanks again.

[Mikendebbie]

Here is a cross section of my steps (yours are similar) and you can see it is basically wide open to the basement. I currently have my vents blocked because the last time we were out a ton of hot air was coming in thru there.

[jsmitfl]

Hi Trevor, we did the sealing of all the places,air could come in like others have mentioned, I also took some filter material and cut it to fit the louvers on the stairs. I just stapled them on the back, it don’t cut all the cool air from passing thru there but it cut down on the drafts we would feel

[cgeis48]

https://www.etsy.com/listing/1021728...vent-cover-for

[jsb5717]

I took a little different approach. Like you, I noticed a lot of incoming air through the vents in the stairs. However, ours was in a summer heat wave. Very hot air billowing into the rig from the stairs.

Since then I got behind the basement wall and sealed all openings in the floor that go into the belly. I used both rigid and spray foam and closed them up. The belly is ducted to keep the tanks from freezing so the holes just seemed useless and served only to siphon air from outside into the coach. I also used rigid foam to seal above the basement wall to keep the furnace area isolated from outside air. I also used some rigid foam to insulate the wall between the furnace space and the living space...mostly for sound control.

I left the stair vents open. And now those vents are truly furnace return air vents only. The coach heats up faster (since it's pulling air from the coach only like my house system) and is quieter. In the Summer the coach also cools faster since there's no more hot outside air being sucked in. I no longer have unwanted incoming air from those vents and there's nothing I have to open or close. It just works more efficiently all year round.