Parent's chalet bungalow - insulation plan.

[TheTeaBoy]

Hello,

 

I am looking to better insulate my parent’s 1970’s chalet bungalow as the upstairs is noticeably warmer than the downstairs. The upstairs also gets very hot in summer and cold at night and the living room downstairs can be very cold in the winter. The living room has large windows and two and a half of the walls are exterior walls, but I hope insulating above will help it retain more heat. I’m not in a position to be redecorating apart from perhaps removing part of the ceiling in the hallway cupboards, to gain access to the flat roof to push insulation into it.

 

 

There is cavity wall insulation and what appears to be the original fibreglass. The fibreglass, (shown in green), is about 60mm thick.  The loft insulation is patchy in places and on the angled roof sections it is pushed up against the roofing felt and has no air gap at either the bottom where it meets the bricks or the top where it reaches the loft. At the top of the angled section near the loft, the fibreglass has turned black, presumably due to moisture making its way from the crawl space up into the loft. I can't see any evidence of mould or moisture on the joists.

 

 

Both the loft and crawl spaces are used for storage. There is airflow inside the crawl space coming from behind a row of bricks where the soffit is out of view. The crawl spaces have bits of plastic sheet and old carpet nailed against the angled roof to reduce the dust coming from the fibreglass. The gap along the roof between the crawl space and the loft (shown in yellow) is 85mm at its narrowest due to battens used to attach plasterboard and is currently stuffed full of fibreglass with no airflow gap.

 

 

I plan to add more insulation on the loft floor (shown in light blue), insulate behind the knee walls (red), the gap below the knee wall to stop drafts under the floor and downstairs light fittings (pink), the crawl space floor and downstairs flat roof (purple), the gap between crawl space and loft, leaving an airflow gap between the roofing felt (yellow), and possibly the rest of the living room ceiling (orange) by pushing insulation into it from the crawlspace.

 

 

Regarding the pink areas, once this has effectively been sealed with insulation stuffed into it, the orange area will no longer benefit from airflow from the crawl spaces. Will moisture from the kitchen and bathroom downstairs be able to pass through this area without collecting and rotting the floor joists? The upstairs has chipboard floorboards with one bedroom having laminate flooring and the other and the toilet a single piece of vinyl flooring each.

 

I’m also considering leaving part of the existing insulation (shown in green) by removing the top part that reaches from the crawl space to the loft.

 

 

I’m not sure what type of insulation I should use for each area. My understanding is that the rigid foam board type is tricky to fit in between joists and the inevitable gaps will affect the insulation properties. Please let me know if my plan meets the principles of insulation and which types of insulation to use in each area.

 

[Sparrowhawk]

Welcome!

 

First your visuals are amazing. I think you rendered them in Twinmotion but how did you draw the building?

 

11 hours ago, TheTeaBoy said:

There is cavity wall insulation and what appears to be the original fibreglass. The fibreglass, (shown in green), is about 60mm thick.  The loft insulation is patchy in places and on the angled roof sections it is pushed up against the roofing felt and has no air gap at either the bottom where it meets the bricks or the top where it reaches the loft.

 

At the top of the angled section near the loft, the fibreglass has turned black, presumably due to moisture making its way from the crawl space up into the loft. I can't see any evidence of mould or moisture on the joists.

 

It's hard to see in the photo but it's either turned black from mold in it or a build up of dirt. The lack of airflow isn't good, so you may want to sacrifice here and later when you can redecorate consider some internal wall insulation over this particular part. Remember that building regs expect a 50mm gap between the roof felt and the insulation, with free flowing air in here.

 

11 hours ago, TheTeaBoy said:

I plan to add more insulation on the loft floor (shown in light blue), insulate behind the knee walls (red), the gap below the knee wall to stop drafts under the floor and downstairs light fittings (pink)

 

I did knee walls last autumn and had significantly underestimated the impact it would have in winter. I used 100mm supasoft insulation as we use these for storage so brush against them. We shall see about summer overheating soon, and whether it's better or worse now.

 

11 hours ago, TheTeaBoy said:

I’m not sure what type of insulation I should use for each area. My understanding is that the rigid foam board type is tricky to fit in between joists and the inevitable gaps will affect the insulation properties. Please let me know if my plan meets the principles of insulation and which types of insulation to use in each area.

 

Others will have the knowledge to make suggestions, but you're spot on re rigid foam boards. For snug fit installation you can put strips of Gapotape down either side of the boards, but it costs an absolute bomb. With the badly fitted ones here I taped them to the joists with aluminium tape, so the insulation value isn't great but they are airtight.

 

Thermal mass is a running joke on this forum but if budgets allow you may want to reach for denser insulation like wood fibre, which slows the progress of heat into the building in summer (see https://www.steico.com/fileadmin/user_upload/English_Media/Content/PDF_Not_PIM_EN/Brochures/STEICO_heat_protection_EN_i.pdf).

[Iceverge]

1 hour ago, Sparrowhawk said:

Thermal mass is a running joke on this forum but if budgets allow you may want to reach for denser insulation like wood fibre, which slows the progress of heat into the building in summer

 

Decrement delay is a better term. It's a factor of the mass, heat capacity and thermal resistance of the material.

 

Heavier materials that are harder to heat up are preferred because by the time the midday sunshine soaks through and heats the inner surface of the material it's already night time and? the heat flow is reversed. The inner surface never gets above room temp.

 

This can be an all in one solution like woodfiber or cellulose or you can get the same effect with a layer of lightweight insulation like EPS coupled to a concrete wall or PIR over a thick layer of OSB and Plasterboard with some concrete roof tiles on top. 

 

 

 

 

[Iceverge]

Back to the first question. What level of destruction are you planning to fit this insulation? 

 

 

[JohnMo]

I would look to use something like RockWool Flexi. It's nice and dense, easy enough to cut and squishes into uneven gaps. Plus it's not massively bad to work with. Another is Knauf Frametherm 32. Similar to above not quite as dense.

[TheTeaBoy]

2 hours ago, Sparrowhawk said:

Welcome!

 

First your visuals are amazing. I think you rendered them in Twinmotion but how did you draw the building?

 

Thanks, I built the model in SketchUp Free. It was fiddly, but I got there in the end.

 

3 hours ago, Sparrowhawk said:

The lack of airflow isn't good, so you may want to sacrifice here and later when you can redecorate consider some internal wall insulation over this particular part. Remember that building regs expect a 50mm gap between the roof felt and the insulation, with free flowing air in here.

 

Okay, I don't know if it will ever be redecorated, I may have to stick something up there.

 

3 hours ago, Sparrowhawk said:

I did knee walls last autumn and had significantly underestimated the impact it would have in winter. I used 100mm supasoft insulation as we use these for storage so brush against them.

 

As my own joists in this area are 70mm deep is there an advantage for me to use insulation that is deeper than 70mm, or is that not how insulation works? I'll have to look into "summer overheating".

 

3 hours ago, Sparrowhawk said:

Thermal mass is a running joke on this forum but if budgets allow you may want to reach for denser insulation like wood fibre, which slows the progress of heat into the building in summer (see https://www.steico.com/fileadmin/user_upload/English_Media/Content/PDF_Not_PIM_EN/Brochures/STEICO_heat_protection_EN_i.pdf).

 Okay, I'll look into that, thanks.👍

[TheTeaBoy]

1 hour ago, Iceverge said:

Back to the first question. What level of destruction are you planning to fit this insulation?

 

Hello.

 

No destruction unfortunately. I understand it is better to also have insulation in front of the joists or have insulating plater board, but all I can do in this instance is insulate in between the joists.

[TheTeaBoy]

1 hour ago, JohnMo said:

I would look to use something like RockWool Flexi. It's nice and dense, easy enough to cut and squishes into uneven gaps. Plus it's not massively bad to work with. Another is Knauf Frametherm 32. Similar to above not quite as dense.

 Thank you for your suggestions. 👍

[Sparrowhawk]

19 hours ago, TheTeaBoy said:

As my own joists in this area are 70mm deep is there an advantage for me to use insulation that is deeper than 70mm, or is that not how insulation works?

 

Yes there is, but 70mm -> 100mm has less impact than 40 -> 70 would have. If 70mm is significantly cheaper use it, else 100mm.

 

Do the soffits have ventilation in them? And is there any ventilation in the loft to let out air that rises? If not, getting that circulation of air from bottom to top is your first task.

 

19 hours ago, TheTeaBoy said:

No destruction unfortunately. I understand it is better to also have insulation in front of the joists or have insulating plater board, but all I can do in this instance is insulate in between the joists.

 

I think you have a massive struggle on your hands with no destruction or redecoration possible. How long do you expect your parents to stay living here? As an alternative is to get an Air to Air heat pump fitted to provide heating and cooling (aircon) winter and summer to give them more comfort.

[TheTeaBoy]

10 hours ago, Sparrowhawk said:

Do the soffits have ventilation in them? And is there any ventilation in the loft to let out air that rises? If not, getting that circulation of air from bottom to top is your first task.

 

My dad drilled some holes into the soffits and there are also some gaps that let in air.

 

 

I can see the cobwebs moving inside the crawlspace so I know there's airflow making its way in. Also in certain weather I feel a draft coming from the crawlspace hatch doors. On one side of the house the crawl space has central heating pipes, if that makes any difference? I can't see the soffit from the crawlspace because there are bricks built up to the roofing felt.

 

 

 

As for the loft I see no obvious ventilation, however at the front of the house there are tiles on the wall from the first floor to the top of the house. I'm not entirely sure if the tiles are up against the breeze-block and so offer some ventilation? 

 

 

The house has been in its current state regarding insulation since the 70s. I can't see any issues with rotten floor of roofing joists unless I'm looking in the wrong places. If I add more insulation will ventilation become more critical?

 

10 hours ago, Sparrowhawk said:

I think you have a massive struggle on your hands with no destruction or redecoration possible.

 

Struggle in terms of installing the insulation, or with experiencing any noticeable benefit? I think I'll be okay with installing it.

 

10 hours ago, Sparrowhawk said:

How long do you expect your parents to stay living here? As an alternative is to get an Air to Air heat pump fitted to provide heating and cooling (aircon) winter and summer to give them more comfort.

 

Well they're both in their 70s now and I'm quite sure the property won't see a change to the heating system in their lifetime. I just want to save them some money on their gas heating bill.

Edited May 12 by TheTeaBoy