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Insulation & moisture control questions?

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PNW_Steve:
Hello Everyone,

I am having serious issues with condensation in two areas this Winter. 

My Wife and I have been spending time at our "getaway" spot for several years and finally moved here full time last year. This has been our first full Winter here. Our "new" home consists of a 36' 5th wheel trailer (3 slides) and an outbuilding constructed on a trailer.

We were rolling along quite comfortably until outside temps dropped into the 30's (F) and lower. The problem is not the cooler weather itself but the condensation that we are dealing with on the windows and poorly insulated exterior walls.

The worst area is the bedroom. The bed is in a slide out so we have exterior walls surrounding the head of the bed. When we wake in the morning there is condensate running down the walls. We are having to pull the mattress out regularly and dry the walls and wipe with bleach to combat the mildew smell. Yesterday my Wife went to get a pair of shoes out of the closet and they had spots of mold on them YUK!!

The only solution I have come across so far in the bedroom is to run the heater and open the windows. It eliminates the condensation but is NOT a good solution.

We have a similar issue in the outbuilding. It is typical 2x6 frame construction with a housewrap then LP siding. The main floor is R19 insulated and sheeted with painted OSB on the interior. However the loft and roof are not yet insulated. In the un-insulated areas I have condensation forming on the housewrap, running down the wall and making puddles at the base of the wall.

I am running two 70 pint dehumidifiers and they appear to be working but don't seem to help the areas that we don't actively heat. The bedroom and the loft.

Along with being less than effective the dehumidifiers are energy pigs.

I know that insulating the loft in the outbuilding will help but I do have some questions. I had intended to fully insulate the outbuilding when we built it but the construction budget fell short. I don't currently have the funds to insulate it properly but I did come across some used 4'x8'x 1.5" foam insulation boards that I can get affordably.

I understand that the root of the problem is warm moist air from the living space contacting the cold/un-insulated walls condenses.

If I use the foam boards to insulate do I want to:

* Cut the foam to fit inside the stud bay and press them all of the way in so that they contact the housewrap?

* Cut the foam to fit inside the stud bay and press them in just flush with the inside edge of the studs leaving an air space between the insulation and the housewrap?

* Use the 4'x8' sheets like wallboard and apply it over the studs?

Any suggestions would be greatly appreciated.

Thanks

Soggy Steve

DamonHD:
First insulate cold spots and thermal bridges where you can: I have been doing internal wall insulation with aerogel at my (London, UK) house.  I am expecting it to help avoid a repeat of the mold problems we had before.

http://www.earth.org.uk/superinsulating-our-living-room.html

Second, consider (single-room through-wall) MHRV to keep your heat but dump the moisture.  We have two and could do with finding a place to put a third near the kids' rooms.  They help a lot especially when it is really cold outside.

http://www.earth.org.uk/MHRV-mechanical-heat-recovery-ventilation.html

Thirdly: a *good* dehumidifier (depending on type I suppose) is a heat pump with an efficiency somewhat better than 1, eg better than plain electric heating, and also really can help.  At this very moment I have switched from dehumidifier to boost on the MHVR to help try some clothes up on a rack in the kitchen.  Both do work.

Rgds

Damon

Frank S:
  IN our RV we experience much the same problem with condensation on the windows enough that it would run down the walls The warmer the inside of the RV was the more condensation there would be . My solution was to just use simple bubble wrap packing on the windows. one year I didn't even bother to tape it to the windows Just pressed the bubble side against the glass it stayed there for quite a few weeks. this reduced the amount of heat required to heat the RV and completly stopped the moisture collecting on the glass.
 De humidifiers have an adverse effect in small overall cubic footage areas. they will dry out the interior air to the point that you will feel colder when the actual tempertures inside is higher. due to evaporation of your bodily fluids also your sinus can become dried out to the point of irritation.

DanG:

--- Quote ---...spending time at our "getaway" spot for several years and finally moved here full time last year. This has been our first full Winter here.
--- End quote ---

Where is 'Here'?  Elevation? Are you in snowpack until May?  PNW is a overly broad clue  :-[

Worse than visible water is humid air leaking into confined spaces and then condensing, any wood structure in the RV is at HIGH risk for permanent damage from damp rot.

Toughing out one winter in your trailer is likely survivable for you both without large lifestyle changes BUT try a second winter and roof & window & slide frames etc. are in jeopardy, and the occupants endangered from mold having more time to bloom in hidden areas. I've seen a mold ring 'fairy circle' nearly four feet across from one thumb print on the inside cap of a vintage Airstream; this season you'll become nose deaf to the trailer but come the heat of summer or next fall and there may be a symphony of odors that could decrease the value/enjoyment of the RV to near zero, ie: if Momma's not happy no one is Happy.

Lifestyle changes? Haw, don't get Damon started about lifestyle changes. I've followed some annual diaries of people over-wintering in serious winter climates in Airstream trailers: Think frozen waterfalls of condensation cascading down walls to reach the floor & on and on in the same vein. Probably the biggest cheat anyone can do is install a small free-standing wood stove, the heat generated helps air carry more moisture before it is drafted up the chimney.

You need a mudroom-porch to have a spot to remove and store over-clothes and footwear. You need to direct power vent bathing and cooking fumes, or better yet move cooking into the outbuilding to keep the airborne nutrients from cooking fumes from feeding hoards of wee-beasties you're living among... I mean if we like the smell of frying bacon then everything else will too. If you've got the power then a heated mattress pad will help with damp trapped in bedding but you still have to 'hang' most of the bedding up to equalize & give up normal sleeping humidity. Damp bath towels dry in the mud-room. Dirty clothes go into a hamper in the mudroom as soon as they are removed. Want to boil pasta? Mudroom hot plate. The lists of changes by the end of the first winter can seem endless.

On the 1-1/2" foam board, maybe option #4! I'd be cross-furring the outbuilding to hang the insulation - this allows air circulation behind the walls top keep occult moisture from breeding fantastic colonies out of what you & yours cough up. I'd also paint the interior facings for two coats of a good flexible latex paint.  You'll need to provide some venting so the exterior wall shell and loft will not see trapped moisture. For the outbuilding remember a vapor barrier is always facing the 'conditioned' air space, done conscientiously the foam will become the barrier.

MattM:
First issue you have to tackle is airflow.  Your airflow is out of control right now.  You are also likely continuing the home lifestyle habits, only in a vehicle.

1.  Skirt your trailer.  I don't care if it's 4mil plastic, get it skirted all the way to the ground then seal it as much as possible.  Ideally you would have insulation on the skirt, but the airflow-proofing is absolutely critical.  RV's are not sealed to the frames, they leak badly.

2.  Seal up walls.  If it's only one winter you could run plastic sheeting over your exterior walls like a green house.  Bad thing is, it's not cold year around, so it'll make your place a hot box when it gets above freezing long.  If you had unlimited budget you could spray closed cell foam into all the exterior walls.  RV's have minimal R and E values by default.

3. Insulation on the roof is key to retaining heat.  Your roof is much smaller surface area than sidewalls.  You're better off getting it up there.

You have to make sure your proper vents, especially hot exhausting, is left open and fire prevention is followed.  Also consider once airflow is restrained, carbon dioxide issues come into play.  Do it smart, but be safe.

Also use insulation where it's helpful.  Cutting pieces to fill voids is poor technique and creates airflow generally.  You must seal every piece!  And try to avoid fiberglass batts.  They actually allow air to permeate them and add next to no value unless airflow is restricted from passing through.

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