Raised Winter Garden - Floor Renewal

Hello everyone,
we have a detached conservatory and would like to renew the floor there and are considering the correct execution regarding insulation.

Current situation:

[*]The support structure consists of a steel beam construction completely lined with wood
[*]The current floor covering is a click linoleum with a thickness of 11mm
[*]The floor is very cold and not walkable without shoes except in summer. Even with shoes, after some time you can clearly feel cold coming from below
[*]The conservatory is connected on two sides to the building/brick wall and has two large doors leading into the living area (kitchen + living room)
[*]Currently, the conservatory is heated with two vertical tube radiators (relatively flat)

Overall floor construction:

[*]I have visualized the entire floor construction as it is today
[*]The glass wool lies in the steel beams between the two flanges, but I could not represent this better
[*]The construction can be seen in the photos

Now the question arises which type of insulation is best suited to make the floor warmer. We can build up a maximum of 50mm higher, i.e. including the floor covering about 60mm are available from the top edge of the OSB. (Higher is not possible, that is the upper edge of the glass profile of the conservatory)
The final floor covering is not yet fixed, we are happy to receive recommendations for this – we can imagine bringing the adjacent living room to the same height in one go and using the floor there as well.

Does it make sense to open the entire cladding etc. from below and change the insulation there or is the effect probably rather small? (my assessment) I can imagine laying a 40mm EPS 035 insulation on the OSB boards and the new floor on top of that. Also conceivable would be to integrate underfloor heating if it can be sensibly integrated into the 60mm build-up including covering. This of course would provide a larger heating surface in addition to the radiators and could counteract the cold floor.
It might also be possible to make changes from above and below, although removing the entire cladding from below is relatively much effort.

I would be very happy to receive advice or tips.

Best regards

Hi,

why do people like to stick to solutions in conservatories that basically ignore the weak spot "cold from below"? Your feeling that a significant effect only occurs when you tackle the problem from below is quite correct. Above all: The glass wool in such an open steel-wood construction often performs much less than expected, as holes, leaks, and thermal bridges are almost never avoidable – the effect of additional insulation on top is then often more cosmetic. If you’ve already opened everything anyway, it would really only hurt once – afterwards the cold is through!

A floor heating system is charming, but with a maximum of 60 mm it turns into a real DIY job with a dry screed solution and thin insulation. You shouldn’t expect much comfort there, because you’re working with little mass and the heat passes through downwards too quickly due to thin insulation. The hard truth: Without relevant thickening downwards, you only get a good bit further if the outside air side is perfectly airtight sealed and permanently dry.

Regarding the covering on top: EPS 035 would be cheap for the insulation, but think about the compressive strength if you want to lay a hard floor covering. With planks or click vinyl on insulation, the wildest things happen if it becomes too soft. Flooring – taste varies a lot here, but a nice, continuous design floor or wood are certainly the most cosy solutions. At the transition to the adjacent rooms, I would in doubt always put a good profile so that there is no tripping edge or rattling joints later.

To me it sounds like you rather don’t want to open everything from below – still: explore how complicated that really would be. Often it is enough to remove individual panels, replace the glass wool cleanly with higher quality insulation boards (for example XPS, format depending on cavity depth) with precisely cut bonding and sealing tapes, to bring significantly more quietness.

Good luck!

Hello Nauer, thank you very much for your input, I will try to address all the individual points:

[*]First of all: I had the feeling that it makes more sense to insulate directly under the floor from above rather than from below, where we can never achieve a 100% solution. The connections are too complicated and also executed too imprecisely to achieve proper airtightness.
[*]So far, nothing has been opened; the plan was at least to open from above for the new covering and from below only if it is really necessary (as you describe it now, it is). It is much more complicated to open everything from below and then cover it again, at least if the structure expands downwards or something like that, because cross beams run underneath and therefore create several compartments. But it is doable...
[*]The conservatory was about 20 years ago once a cantilevered wooden balcony. My parents live in the house and back then we demolished the balcony and built the elevated construction ourselves. We are not unskilled craftsmen, but it was done "the way it used to be done" without giving extreme thought to the cold upwards. The conservatory builder also did not really add value..
[*]I understand compressive strength - but there are insulation boards that you can lay a floor covering directly on, or is a solid layer like OSB or similar always necessary underneath if it is not screed? A transition to the living room is currently unproblematic, as there is a door with a threshold through which you have to step anyway. (5cm) That was previously the outside door to the balcony, which now simply always stays open.
[*]Moisture was not measured, but there were no drops noticed either. We had several leaks over the years, but they came from outside through the seals of the panes. We have now replaced 3 panes and several seals, so fortunately no water comes in anymore.. (The conservatory builder never was able to fix the problem and wasn't motivated either..

Now about the change of insulation material, if that is an option. On which level should the whole thing reasonably be insulated? For example, we cannot insert anything into the spaces between the beams because the beams are all completely covered on the end faces with metal sheets from the conservatory and on the other side the house wall, so inserting a full panel there will not work. I would like to sketch this to understand it but I’m not exactly sure at which point it makes sense. It would also be conceivable to start directly above the beam towards the room with 2cm, then OSB and then 4cm again under the floor. My feeling is that the cold beams would need to be decoupled upwards if you do not manage to shield all cold from below to the beams.

Additionally, the idea came up today, if necessary, to fill the entire intermediate space as much as possible, whether a bound aggregate is possible and sensible.

[*]Completely dismantle floor structure including OSB
[*]Cover steel beams below with OSB, I still have to think about how to properly fix these panels. Additionally, attach/glue a foil underneath the beams.
[*]Completely fill bound aggregate (e.g., Thermobound EPS 160) up to the upper edge of the beams. This would have a thermal conductivity of 0.056 W/mK and about 180kg/m³
[*]The room is about 17m² in size and the beams are 14cm thick, resulting in approximately 2.4m³ and thus ~450 kg (minus the volume of the beams). We would still have to check whether the beams could adequately bear the weight.
[*]Above that, a rigid insulation above the beams but below the floor structure with higher insulation value and as a compressive layer for the floor structure.

With this, at least the intermediate space could be completely filled and you would not risk missing any connection points. The processing is relatively simple, but of course significantly more effort compared to "simply" laying boards on top.

This just came to mind because I have often seen this below underfloor heating in the pipe level, over which insulation + heating + screed were then laid. Cost-wise this is about 100-120€/m³ and thus relatively manageable for the area if it makes sense.

Best regards