Thermally Upgrading Suspended Timber Floors with Natural Insulation
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- Опубліковано 11 лип 2024
- Dave Judd explains what a suspended timber floor is and how this type of floor can be insulated with sustainable natural insulation. The end result is fully insulated and airtight to maximise the thermal benefits, provide a more comfortable living space and reduce energy bills.
The video shows how an airtight vapour control membrane can be used over the joists to prevent warm humid air escaping into the floor-void underneath where it may condense on the colder surfaces and cause problems. Dave also explains how a windtight breathable membrane like Pro Clima Solitex Plus can be installed to hold the insulation in-place and prevent any cold draughts entering the insulation and room above.
The combination of 100% coverage natural insulation, an airtight breather membrane and a fully windproof breather membrane on the underneath, ensures maximum thermal performance and energy savings in your home.
A detailed installation guide is available on our website:
www.ecologicalbuildingsystems...
For those wondering how you would incorporate underfloor heating when thermally upgrading a suspended timber floor: • How to Add Underfloor ...
We did one room last winter as a proof of concept with considerable improvement. Checked in spring and like new, just finishing the rest of the house.
Thank you for your feedback, that's great that you are achieving better comfort levels!
What a fantastic video, with the clarity of your explanations and comprehensive guidance and the way you’ve addressed all the queries you have inspired faith that this is the way to proceed, I’m looking forward to the project, thanks
Glad it was helpful!
nteresting and super detailed - thank you. One point - you refer to seeking to avoid condensation. My thinking is that the main concern is not condensation but sustained elevated Equilibrium Relative Humidity (ERH) values, which can lead to sustained high levels of Equilibrium Moisture Content (EMC) in hygroscopic materials, such as joists.
In other words, problems can arise even when the temperature remains above the dew point, and even if, therefore, condensation does not occur. With the reduction of heat leakage into the subfloor, the average temperature will now be lower and so the RH will be slightly higher, on average. The vapor control layer will prevent water vapor from moving into the sub-floor environment from the occupied spaces (it will prevent this moisture moving to the cold side of the insulation). However, there are other sources of moisture, especially from a slab laid on soil, or from bare soil, which could lead, with the now lower temperatures, to sustained elevated RH values. If these exceed well over 85% RH then the EMC of the joists could remain elevated well above 20%, to a level sufficient to promote fungi growth. It would be interesting to monitor the moisture levels of the joists where this system is installed with soil or slab-on-soil subfloor. It would take many years for rot to arise and cause structural damage. Another way this could be predicted would be if the RH was monitored within the sub-floor space perhaps by a data logger (or IoT RH sensor) put into the void through an air brick.
Just a thought...
The potential risks outlined can be overcome by ensuring adequate ventilation in the subfloor joist zone and also only use this system if the zone below is relatively dry. If the subfloor zone has a high water table and is constantly wet then we would not recommend using this system.
Please see our blog:
www.ecologicalbuildingsystems.com/post/suspended-timber-floor-insulation-best-practice-installation-guide This explains the precautions and checks necessary to determine the suitability of the system.
Thank you for this video and the guide on your website, from much research this is the method we are going to go for when we replace our floors in the coming year
Thank you, really glad you found it useful.
Temp profile last winter showed suspended floor was 8 degree Celsius below room temp. So about to start two floors so video gave excellent instruction on build up. Also reminded me I forgot to order pipe grommets for rad pipes, oops! Will let you know how I get on.
We're happy to help and always pleased to hear about your project. If you haven't already seen our floor insulation blogs, do take a look. We have detailed guides and downloads on those pages to go alongside this video. www.ecologicalbuildingsystems.com/blog/floor-insulation
Just one query, the manufacturers of p5 chipboard flooring all say to glue there floors to the joists as well as screwing ,but this is not possible now with the membrane, would sealing the floor with a paint on sealer solve this problem
Ordered all the materials after seeing the video! Would be interested in what's the best approach when dealing with vents that go near the joists.
Designed vent openings in the sub floor void are very important and they should not be obstructed in anyway likely to reduce airflow below the insulated floor. Hope that helps.
Fantastic video, thank you very much for sharing! I will be sharing with my own network.
Is doing this DIY the only option really? Do you have(or are you building) a competent installer network that has been trained to install a floor retrofit in this manner using these products?
Thanks again.
Please contact us on our website. Our sales team should be able to suggest someone in your area. www.ecologicalbuildingsystems.com/contact
Great video. It mentions at the start of the video that heating pipes under the floor should be lagged - therefore shouldn't the pipe in this scenario need lagging? When the floor boards are then re-laid, how are the membranes prevented from being penetrated by the fixings?
So glad to hear you liked the video. Yes, all heating and water pipes must be lagged due to the underfloor area being colder once you prevent heat "leaking" from the living space above. We may have missed a pipe during the filming as we didn't complete it in one take! For the fixings, so long as the screws or nails cleanly penetrate the membrane, are tight, do not miss the joist and are not removed or reinserted, the airtightness will not be affected.
great explication. thanks
is the crawl space ventilated in winter as well?
Hi @christophervarady-szabo1547. The timber suspended floor will be permanently ventilated all year round via the air bricks in the external walls. Hope that answers your query. Let us know if you need any further information. Thanks.
Awesome video. Can we apply it to our suspended floor (ground level) house in Melbourne, Australia?
So long as the sub floor joist zone is adequately vented and is relatively dry (no water pooling in the ground below) then you can use this system in a Melbourne climate.
Thankyou. Great explanation.
Can you use the breather membrane as described in your video and PIR board between these joists sit on the breather? The reason is to allow underfloor heating pipes to clip onto the pir board.
The PIR boards would have to be cut precisely in order to achieve a full fit with the timber joists as any gaps between the timbers and the insulation leads to closed loop thermal bypass (i.e. the insulation doesn’t work as well). Our recommendation is to friction fit Thermo Hemp Combi Jute flexible insulation to a thickness of 20mm below the top of the floor joists and then fit aluminium winged trays and sit the water pipes onto this. See an image of this here: www.ecologicalbuildingsystems.com/suspended-timber-floor-underfloor-heating-examples
Yes I have seen similar examples with aluminium trays, but I have read this is a poor retainer of heat compared to screed biscuit mix and not recommended future heat pump. Would would you suggest for a base to sit on the JUTE or wool or whatever for the pipes to clip to to allow a screed?@@EcologicalBuildingSystems
This is fantastic. Can you do one for method 2? We went the original boards and its freezing. I'd like to tackle it from the cellar
We are working on new video content all the time, but currently don't have a video covering the other installation method. Method 2, where the system is installed from underneath (floorboards remaining in place) is detailed on our blog here: www.ecologicalbuildingsystems.com/post/suspended-timber-floor-insulation-installation-underneath
@@EcologicalBuildingSystems I have lathe and plaster and can't put the membrane and insulation to the wall as air needs to get up between the walls , I was just going to put eco insulation between joists without membrane , if it helps to keep rooms a few degree warmer it would help as it's really cold , 9 - 10 c on walls and floor , how much to get a company to do it from underneath as my crawl space is about a metre high , the joists are fine but since a new roof the loft is really cold and draughty which it wasn't before , the walls I will deal with at some point , so my question is can I just put insulation underneath between joists ,thanks
Without the Solitex Plus membrane below, there will be air flowing through the insulation which will greatly reduce the effectiveness of the insulation (convective thermal bypass). In this situation, we would suggest both floor and wall be upgraded at the same time. Please see our blog for posts on floor and wall insulation and if you have any questions, get in touch via the contact page on our website.
@@EcologicalBuildingSystems cheers ,
If not fully taking the floor apart is it ok to work from the bottom space, reaching up tucking insulation in fresh where it may need it then attaching a permeable layer to the underside of the joists?
It is possible to install from underneath. The method is described in detail on our website here: www.ecologicalbuildingsystems.com/post/suspended-timber-floor-insulation-installation-underneath
that's what in US is called a crawl space. Another solution is being suggested to incapsulate the crawl space with a membrane to prevent moisture from the ground and more importantly the radon gas reaching the living space. The wall of the crawl space are insulated, as well as, in cold climates, the floor joints, just like in this video. Any moisture is also removed with a dehumidifier.
Laying a 1000 gauge polythene radon barrier membrane on the ground below the ventilation zone below the floor joists is a good idea not just from a radon protection viewpoint, but also prevents excessive moisture from coming up into the vented zone from below ground. If there is sufficient ventilation in the zone below the floor joists (air bricks) then dehumidification (apart from perhaps some initial dehumidification) should not be necessary.
😅😅in Deutschland heißt das auch Kriechkeller. Aber sehr selten baulich umgesetzt. Unterströmte Flächen zählen 2x so schlecht in der wärmebilanz
@@EcologicalBuildingSystems Where does the excess moisture go if a ground membrane is installed - is there a danger it will make the walls wetter, especially if the crawl space ground level is below the outside ground level (which is surprisingly common in older houses)
@@furniss32also interested in knowing this.
The zone below the floor joists must be adequately ventilated. If the crawl space is below external ground level then there are options such as telescopic vents that can be used.
If the underfloor space is unheated, should there not be a Thermal Break somewhere? Great video. Thanks for posting.
This method details how to upgrade the floor "from above". If you have access to the underneath, please see our other method that uses Gutex Mutitherm woodfibre boards to address thermal bridges. See this blog for details:
www.ecologicalbuildingsystems.com/post/suspended-timber-floor-insulation-installation-underneath
I am assuming we can install under floor heating over this form of insulation. We are hoping for UFH between joists to keep floor height low so I’m assuming we therefore just start the insulation level a little lower to leave space for UFH
The system is compatible with underfloor heating typically installed above the joists. Please contact our technical team via the contact page on our website to discuss the method.
How similar / disimilar are the membranes from those used in roofing?
And then, in theory, could you apply a similar system between roof rafters for further house insulation?
(Currently in the process of trying a renovate and sensibly modernise a cold 1940s house, thank in advance for any advice!)
Hi @nottagepie. The same insulation could be used on a pitched roof application. In this case the SOLITEX PLUS would be outside (with a counter batten above this if you plan to full fill the rafter void) and we would recommend changing the DA to pro clima INTELLO PLUS on the inside. The same pro clima tapes and seals can be used. Hope that helps.
Is there any issue with nails and screws from fixing the floorboards going through the vapour barrier?
The nails and screws need to be fixed to the joists tightly and not removed. Basically, when the nails/screws penetrate the membrane cleanly and all of them go directly into a joist it will be airtight. You must be extra careful not to miss the joist with a screw or nail. Any screws/nails that miss a joist mean you will have to remove the floorboard and patch the hole in the membrane with Pro Clima Tescon Vana airtight tape and try again. So just make sure you don't miss the joist with your fixings!
Unfortunately none of the local builder where I live (South East London) provide underfloor insulation. Some provide spray foam insulation. Are you able to put me in touch with someone who provides underfloor insulation using the same method as the video?
Please contact us for recommendations. www.ecologicalbuildingsystems.com/contact
I'm thinking of insulating from below, without removing floorboards. The method (2) you describe involves fixing strips of vapour permeable membrane under the floorboards and sealing them to the sides of the joists with Orcon F. Would it be wrong to instead run a continuous, wider length of the Proclima DA membrane across the underside of adjacent joists (and up against the floorboards), effectively placing the joists on the internal side of a continuous vapour permeable membrane, together with the floorboards (then installing the bulk insulation, then the Solitex Plus)? It just seems technically simpler, but I wouldn't want to compromise the joists with excessive moisture, for example.
Hi @yvesk876. Unfortunately, it is not possible to run the Pro Clima DA across the underside of the floor joists and then up the side of the joists and then across the underside of the floor boards. The reason for this is that Pro Clima DA is an Airtightness and moisture vapour control membrane and this would risk trapping some moisture at the bottom of the joists - hence the reason for cutting strips of the DA membrane and sealing to the underside of the floorboards and part way down the sides of the joists (and not underneath). Hope that helps.
Would it be possible to staple the permeable membrane to the underside of the joist . It would use less material but would enclose the joist. Is that bad? Would it reduce air flow around the joist and therefore result in rot? Or would it help maintain the temp of the joist in a dryer environment?
Hi @fredhawkey380. It is possible to stable and tape and seal the SOLITEX PLUS diffusion open membrane below the joist which will allow any vapour to diffuse to the vented cavity below. We would also recommend applying support battens below the membrane to support the weight of the insulation over time. Of course, it is still recommended to apply the sealed airtightness and vapour controlling pro clima DA membrane on the warm side of the natural fibre insulation if you are applying this from above. Hope that helps. Thanks for the comment.
@@EcologicalBuildingSystems cheers . I've just realised why u do it like that. My crawl space is so shallow I couldn't get the drill underneath. Less awkward from the top. 👍
Does adding a vapour barrier on top hinder the ability of an older property to release internal moisture and encourage damp/mould issues. Can you add a second wind tight breather membrane instead of the vapour barrier to encourage less internal moisture build up?
The vapour control membrane above the insulation prevents warm humid air escaping to the cold floor void underneath where it can condense on the cold timber surfaces and potentially cause structural damage from condensation and mould - this is a vital component of the system. The floor void, must also be correctly ventilated and free from moisture issues. Before proceeding with the installation, it is essential to check the moisture levels under the floor. Joists must be dry and any rotting timber must be replaced before beginning work. Please contact us for advice if the ground/soil below is visibly damp or wet or likely to flood. We have a downloadable installation guide here with full details: www.ecologicalbuildingsystems.com/post/suspended-timber-floor-insulation-best-practice-installation-guide
@@EcologicalBuildingSystems Good answer Eco!
Good question Matthew!
What other types of insulation can you use? Can you use Steico Flex 036 wood batts?
Hi David. We supply Gutex Thermoflex for this installation, there's some good info on it here www.ecologicalbuildingsystems.com/product/thermoflex
Yes, I've used Steico flex. Did first room 8 years ago. 140mm. Made the world of difference.
I like the concept and thought of it myself, but there is controversy over a water tight membrane next to the subfloor acting as a means to hold water or condensation here in the USA ( location North vs South ). Have you experienced any issues due occupants creating a source
…. Of water or appliance leaks?
The key aspect here is that the void below the floor needs to have sufficient air flow ventilation. If the soil below the floor is often damp then laying a polythene membrane on top is beneficial in reducing rising moisture vapour from the ground. In other words, for a consistently damp sub soil then combining polythene with ventilation is the best solution.
A little confused when you described the Solitex Plus to be a "breather membrane" that is also "airtight". 🤔 Can you tell me if is it Breathable?.... Or Airtight? aka a "Vapor Barrier".
Cheers
Hi @timbramm4650. Solitex Plus is both breathable and airtight. Breathability refers to the movement of moisture and doesn't affect the airtightness. It might be good to think of it like this, human skin can sweat but it doesn't allow air in. Solitex Plus manages moisture by transferring water vapour and doesn't need any air movement beneath or through to transport the moisture. Hope that helps.
@@EcologicalBuildingSystemswhat a great answer
What’s the u value of this floor buildup assuming 100mm joists?
The U-value of any particular floor depends upon a few factors, such as the timber percentage and the perimeter to Area (P/A) ratio of the floor. Based on floor joists being 100mm deep and using the Hemp-Jute insulation, as shown in the video, this usually achieves somewhere in the region of 0.25 W/m2K. Hope that helps.
Surely a plastic DPM can be used instead of the green membrane or is this a big no? Thanks
I’d of thought so.
We would not recommend using a polythene vapour barrier here. The breathable floor system benefits from a vapour control membrane as it allows for some breathability from inside to outside. DA is also more robust, easier to staple and tape, and means the full Pro Clima airtightness system is used so you get all the benefits of the Pro Clima system warranty.
Can I use tescon no1 tape instead of tescon vana tape for sealing membrane overlaps?
Yes, all the Pro Clima tapes like Tescon No.1, Tescon Vana, Uni Tape and Tescon Invis can be used on membrane overlaps. No.1, Vana and Uni Tape have all been independently tested (via accelerated aging) to show they remain airtight for at least 100 years - so No. 1 would be a good choice!
@@EcologicalBuildingSystems Can the same tapes you mentioned be used to secure the breathable membrane & the damp proof membrane to the wall? (with primer). Would be good if a single product could get all those jobs done.
The best tape for sealing low surface tension membranes such as DPM polythene type membranes is Moll Compego tape. See our website for details of this tape. For the Pro Clima membranes, you would use Pro Clima Compego Solido SL to seal them to the wall (with primer).
What sort of u value does this achieve?
Hi @TheTravelTipsGuy the u-value is influenced by a number of factors including floor dimensions, timber depth and spacing and type of insulation used . Please send your details and we will be happy to provide a solution and calculation for your records.
4.18 6 materials in shot, and the flooring 2 or 3 just out of shot = this is another part of industry thats needs to get its act together and innovate 'an engineered lay 1 item on the foundations' way of building.
As a retrofit solution, the products here work around the existing fabric of the building to achieve an improved thermal performance. We are all for innovation in the industry and have designed this retrofit floor insulation system to be as simple as possible.
Jobsworth!
Our 20th century meddling/improvements to our Victorian houses led to unintended problems.. and still do.. Back then when coal was king (and cheap) we actually need air coming through the carpets to aid combustion.. We made the best with what was available.. When gas was introduced I believe it became mandatory to have a wall vent. The Victorians used to put newspaper under their carpets or horsehair underlay.. They had lots of horses then.. It seems every material has its benefits and down sides.. Perhaps rodents like Hemp.. Eating.. not smoking.. who knows.. I would have thought a MultiFoil type would have been easier to install and less absorbant..
The hemp and jute natural insulation has no nutritional value for vermin or insects so wouldn't be an attractive food source.
The hemp/jute insulation is breathable and absorbs humidity which is key to the effectiveness of this solution. It is also a flexible insulation so it is easy to install with no gaps which prevents closed loop thermal bypass. Dave explains the benefits and properties of the insulation in more detail in the video.
Yes. And don't forget they sent kids up the chimneys in those days!
Great detail, unfortunately the only item not addressed was the thermal losses through the floor joists. This can be done using a thin layer of cork board or wood fibre board before the floor finishes. It dose mean doors will need to be altered nut no point in doing all this and falling at the end.
Thanks for raising this important point. In our U-value calculations using 100mm Thermo Hemp Combi Jute between 100mm timber joists (in accordance with EN ISO 6946 and BR443), we include the correction factor for the floor joist repeating thermal bridges and find that where the perimeter-to-floor ratio is