Insulate extension in summer cottage/lake cabin

[Marcus.lkpg]

Hello,

Like many other thread starters about conservatories and insulation, I am now seeking tips and advice. I will insulate an extension in the summer cottage that has been used for about 15 years as a dish room and turn it into a bathroom with a shower cabin and incineration toilet. The cottage is located near water and is only used during late spring and summer, otherwise it remains unheated.
The extension stands on pillars and currently has regular decking of pressure-treated wood as the floor, exterior wood facade as walls, and a simple sheet metal roof. In other words, the simplest possible extension.

Now the entire extension needs to be insulated and integrated with the rest of the cottage. Since the cottage is by a lake, one starts to wonder how this should be done in the best way regarding moisture. My considerations, which I hope some kind soul can help me with, are the following:

1. Floor insulation; is it polystyrene that is needed to avoid too much moisture? The floor needs to be raised about 15 cm to be level with the rest of the cottage, and currently, there is decking of pressure-treated wood. The easiest would be to place the polystyrene directly on the decking, but I read somewhere that pressure-treated wood should be avoided as it smells strange and can be unhealthy...? How thick should the insulation be, is about 10 cm enough? I would prefer to finish with a lacquered nice wooden floor but understand that vinyl flooring might be smarter from a moisture perspective?

2. Wall insulation; currently, the walls consist of a simple wood facade. Can you insulate with polystyrene here as well? If so, perhaps no plastic is needed, and facade-air gap-polystyrene-panel might work okay?

3. Roof insulation; Is the approach different here? Could it be smart to use some other insulation than just polystyrene, or is that overkill considering the cottage is only used during the summer months?

Many thanks in advance for all helpful tips and suggestions,

Best regards

 

[surris]

Hello,

Like many other starters of threads on sunrooms and insulating them, I am now seeking tips and advice. I will be insulating an extension at our summer house that has been used for about 15 years as a utility room and now turning it into a bathroom with a shower cabin and a combustion toilet. The cottage is located near water and is only used during late spring and summer; otherwise, it remains unheated.
The extension is on piers and currently has regular decking of pressure-treated wood as flooring, wooden exterior facade as walls, and a simple metal roof. So, it's the simplest possible extension.

Now the entire extension will be insulated and integrated with the rest of the cottage. Since the cottage is located by a lake, one starts to wonder how this should be done in the best way with regard to moisture. My thoughts that I hope some kind soul can help me with are the following:

1. Floor insulation; is styrofoam the way to go to avoid too much moisture? The floor needs to be raised by about 15 cm to be flush with the rest of the cottage, and currently, there is pressure-treated wood decking. The easiest thing would be to place the styrofoam directly on the decking, but I read somewhere that pressure-treated wood should be avoided as it smells strange and can be unhealthy…? How thick should the insulation be, is about 10 cm enough? I would prefer to finish with a nice lacquered wood floor but understand that vinyl flooring might be smarter concerning moisture?

2. Wall insulation; today the walls consist of a simple wooden facade. Can you insulate with styrofoam here too? If so, maybe no plastic is needed, but facade-air gap-styrofoam-panel might work okay?

3. Roof insulation; Do you think differently here? Would it be smart to use some insulation other than styrofoam, or is that overkill given that the cottage is only used during the summer months?

Thank you very much in advance for all helpful tips and suggestions.

Best regards

You should not use styrofoam anywhere…it is extremely flammable and should only be cast or built in with fire protection. The pressure-treated wood must be removed; it should not be indoors. If it's only going to be used in spring/summer, 100mm of insulation in the floor/roof is absolutely sufficient, and 70mm is enough for the wall. You should, however, keep a little bit of heat on for the rest of the year, not under 10 degrees. Mineral wool for insulation everywhere; since it will be a bathroom, you'll have a vapor barrier in the construction as well.