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Thermal conductivity, often denoted by the greek symbol λ ,measures of how easily heat flows through a material, independent of the thickness of the material in question.
The lower the thermal conductivity = the slower heat will move across a material= good
It is measured in Watts per Metre Kelvin (W/mK).
0.008 W/mK for vacuum insulated panels = very good = retains heat
0.061 W/mK for certain types of wood fibre = not so good looses heat
R-Values
The R-value is a measure of resistance to heat flow through a given thickness of material.
The higher the R-value the better its insulating properties.
The R-value is calculated by using the formula
Where:
l is the thickness of the material in metres and
λ is the thermal conductivity in W/mK.
The R-value is measured in metres squared Kelvin per Watt (m2K/W)
“The R-value is therefore a relatively simple way to compare two insulating materials if you have the thermal conductivity for each material. It also allows you to see the impact of adding thicker layers of the same insulating material.”
But ” R-values only take into account conduction. It does not include either convection or radiation.”
so on to
U-Values
takes into account all factors and is the most reliable method of measuring but it is more difficult to calculate.
“The U value of a building element is the inverse of the total thermal resistance of that element. The U-value is a measure of how much heat is lost through a given thickness of a particular material, but includes the three major ways in which heat loss occurs – conduction, convection and radiation.”
To Conclude
- Thermal Resistance = how fast heat passes through a material independent of thicknessshown as λ / W/mK .The higher the number the better
- R-Values takes the thickness of the material into account – so thermal resistance in more detail. (m2K/W) Again higher is better.
- U-Values.
- The U-Value is the most accurate measurement of a material’s insulating ability, In this case THE LOWER the number the better.
Very good read HERE
Why should I insulate and where?
A useful ARTICLE HERE.
For our van, we used Elephant Bark 1/4″ rubber (also called Stall Mats) as an MLV-type layer on the floor. We isolated it from the stock wooden van floor using a layer of LowE foil-faced closed cell foam. The full stack of materials gives us a good combination of heat and sound damping.
On the walls, we used DB2-4walls. It’s a .75lb/sf. product, 1/8″ thick. We didn’t use it throughout the van, but we did put sheets of it behind the door panels before we re-applied them.
(thats 6.35mm thick!)
From a useful ARTICLE.
used rubber on the floor
- Rubber rolls can be installed in minutes with 2-sided carpet tape, no messy adhesive needed
- Rubberized flooring made from abrasion and wear resistant 100-Percent USA produce recycled rubber
- Extremely durable which makes this product ideal for deck flooring or dog mats for kennels
- This rubber flooring roll is an excellent way to turn your concrete floors into comfortable, warm, and protective rubber surfaces
- Ideal for use as: sports flooring, garage floor covering, basement flooring, gym equipment mats, and horse trailer floor covering
First, let’s see where, on average, the most heat leaves the house, what the target insulation value should be and what measures are appropriate. This is found in Table 1.
| Building feature | Heat loss (%) | Target U-value (EPC Band B) | Possible solutions | |
|---|---|---|---|---|
| Table 1: heat loss through building elements, target insulation levels and insulation solutions | ||||
| Walls | 35 % | 0.15 | Cavity, internal or external wall insulation | |
| Windows and doors | 15 % | 1.6 | Double/triple/secondary glazing / shutters and curtains | |
| Roof | 25 % | 0.10 | Pitched, warm deck or cold deck roof insulation | |
| Floor | 15 % | 0.15 | Floor insulation | |
| Gaps, cracks, draughts | 10 % | |||
Image (click to zoom) Material K-value (W/mK) Notes
| Material | Depth |
|---|---|
| Table 2: depth of insulation required to reach a U-value of 0.15W/m2K | |
| Expanded polyurethane | 130 mm |
| Unfaced polyurethane | 160 mm |
| Rockwool (60 – 100kg/m3) | 195 mm |
| Glassfibre slab | 205 mm |
| Expanded polystyrene | 215 mm |
| Mineral wool | 225 mm |
| Flax | 230 mm |
| Expanded Corkboard (110kg/m3) | 240 mm |
| Glass fibre quilt | 240 mm |
| Cork slab (160kg/m3) | 250 mm |
| Woodwool board | 250 mm |
| Cellular sheet glass | 280 mm |
| Foam glass (140kg/m3) | 305 mm |
| Cork slab (140kg/m3) | 325 mm |
| Foam glass (130kg/m3) | 330 mm |
| Material | Depth |
|---|---|
| Table 2: depth of insulation required to reach a U-value of 0.15W/m2K | |
Table 5: Summary comparison of different insulation materials
Organic sources
These have absorbed carbon from the atmosphere and so are more climate-friendly
Sheep’s wool batts and rolls 0.038 – 0.043 Can absorb some moisture whilst remaining efficient
Wood fibre batts 0.038 – 0.043 Good for most walls, ceilings, roofs, timber joisted floors.
Cotton-based batts and rolls 0.038 – 0.043 Best for horizontal surfaces.
Cellulose (loose, batt or board) (e.g. Warmcel, Homatherm) 0.038 – 0.040 Recyclable, renewable, made from finely shredded newspaper, easy to install, best for horizontal services.
Flax batts, slabs and rolls approximately 0.042 Hard to obtain and expensive.
Hemp batts 0.043 Relatively expensive.
expanded-corkboard Expanded Corkboard (e.g. Amorim, Korktherm, Westco) 0.040 – 0.050 Commonly used as underlay under hardwood and ceramic floors.
Wood fibre board (eg. Pavatex) 0.039-0.46 Good for wall and pitched roof construction
Hempcrete (e.g. Hemcrete, Canobiote, Canosmose, and Isochanvre) 0.12 – 0.13 Made of hemp shiv with a lime matrix. High elasticity and vapour permeability. Used for external wall insulation. Typical compressive strength 20 times lower than low grade concrete. Density: 15 per cent of traditional concrete.
Naturally occurring minerals
Usually environmentally ok but some have high embodied energy – see Table 3
Aerogel (e.g. Spacetherm) 0.013 Flexible sheets and laminates, a type of glass and composite materials including plasterboard and sandwiched within PVC panels. Expensive but useful where width is limited as performance is so good. Not breathable.
Fibreglass mineral wool batts and rolls (BSI kitemarked available) (e.g. British-Gypsum Isover, Knauf, Superglass) or Fibreglass board (e.g. Isowool, Dritherm) 0.033 – 0.040 Made from molten glass, sometimes with 20 to
30 per cent recycled content. The most common residential insulant. Usually applied as batts, pressed between studs. Most include a formaldehyde-based binder – exceptions are beginning to appear.
Mineral (rock & slag) wool batts and rolls (BSI kitemarked available) (e.g. Rockwool) 0.033 – 0.040 Used for loft and cavity wall insulation.
Foamed glass slab (e.g. Foamglas) 0.042 High, durable compressive strength, non-permeable. Needs bitumen or synthetic adhesives to install.
Perlite 0.045 – 0.05 Naturally occurring volcanic glass that greatly expands and becomes porous when heated sufficiently. Must be installed in sealed spaces.
Exfoliated vermiculite 0.063 Clay-based, otherwise like perlite
Multi-foil insulation (or ‘Radiant barriers’) disputed Thinness makes it ideal for places where little width is available. Made from non-renewable petrochemicals and aluminium. Can have poor airtightness. Expensive, vulnerable to being punctured, which will render it useless.
Fossil fuels
These have emitted carbon to the atmosphere during manufacture. Avoid unless you don’t have the space or budget for natural products. All manufactured at high temperatures, derived from fossil fuels. Extremely high embodied energy. Non-breathable, so may cause damp problems.
Phenolic foam board (e.g. Kingspan Kooltherm) 0.020 – 0.25 For roofing, cavity board, external wall board, plaster board dry linings systems, floor insulation and as sarking board.
Expanded polystyrene board and beads (EPS) 0.032 – 0.040 Beads are used primarily in masonry cavities.
Extruded Polystyrene board (XPS) (e.g. Kingspan Styrozone) 0.028 – 0.036 Very high compressive strength.
Polyurethane/polyisocyanurate board and foam
(e.g. Kingspan Therma) 0.02 – 0.033 Foam or rigid board. Foam is sprayed in at high temperatures; within seconds it will expand by over 30 times giving a seamless rigid covering. Good for plugging gaps or leaks. High compressive strength.
Eco-wool (e.g. non-itch) – batts 0.039 – 0.042 Alternative to glass wool, made from 85 per cent recycled plastic. Comes in rolls or slabs. Suitable for loft and stud walls.
Structural Insulated Panels (SIPs) variable approximately 0.040 A building method using pre-cut expanded polystyrene (EPS) or extruded polystyrene foam (XPS) to erect an airtight structure quickly that eliminates thermal bridging.
Expanded Cork
TECHNICAL CHARACTERISTICS
Thermal Conductivity: 0.036-0.38 W/mk for a declared value of EU label 0.04 W/mk
Thermal Resistance: R-3.6 to R-4.2/inch, declared value for EU label of R-4/inch
Density: 7.0-7.5 lbs/ft3 or 100-120 Kg/m3
Perpendicular Face Resistance:60 Kpa or 8.7 PSI
Compression Resistance: 10% at 100u Kpa (14.5 PSI)
Permeability:
- 1 1/2″ thickness:2.15 US perms
- 2″ thickness: 2.04 US perms
- 4″ thickness:1.26 US perms
Maximum Moisture Content: 8%, with water absorption declared at 0.5 kg/m3
Longitude Tolerance: +/-0.1 to 0.2″ or +/-3 to 5 mm
Thickness Tolerance: 0.04 to 0.1″ or +/-1 to 2 mm
Fire Resistance: Euro Class “E”
Why can insulation cause damp?
As you’ll know, insulation is designed to slow down heat transfer, keeping warm air in and cold air out. However, the more airtight your house is, the less natural ventilation it gets – and airflow is key for maintaining a healthy level of humidity indoors.
What people are often not told by insulation installers is that warm air holds more moisture, and this has got to go somewhere. If insulation means this water vapour cannot escape through walls or ceilings, it sinks into the fabric of the building, or its contents. It is important therefore to counter increased humidity with increased ventilation. Make sure to use extractor fans and/or open windows – especially when you’re doing something that creates a lot of steam, such as showering or cooking.
Damp after loft insulation
So you only “decided to insulate the floor of the space, rather than the roof. This is because there is very little point paying to heat your attic – and the nature of heat rising means that a lot of heating escapes up there! Insulating this space effectively will keep warm air in the main body of the house below, and your loft will get pretty cold as a result. As long as it is dry up there, this shouldn’t be an issue if you’re only going up now and then to grab boxes. Potential problems can arise when damp air gets into the space and reaches its dew point in the low temperature, condensing on surfaces, (and in some cases, the insulation material itself). Damp can set in and lead to mould, which can be tricky to get rid of. This is why it’s important to have adequate ventilation in the roof, and make sure any insulation doesn’t cover the vents. Something else you should consider carefully is the material you choose, as their abilities to resist damp vary hugely. If you use an insulation material that is not breathable, it soaks up water and keeps it there. Fibreglass, for instance, is easily soiled – and once it’s wet, it stays that way. Pure sheep wool, in comparison, helps regulate humidity in the air wherever it is. It can be more easily dried out, and its thermal performance is not affected when it holds water vapour.
Never before has carpet underlay been this good.Swaledale our heavy weight pure new wool carpet underlay manufactured from 100% pure Swaledale wool. It is suitable for heavy domestic & heavy commercial use, ideal for all areas in your home especially stairs.Please Note: This product is now made with 100% Swaledale wool and has a new improved Jute scrim which is ideal for anyone wanting a totally natural product.
KEY FEATURES OF OUR OPTIMAL SHEEP WOOL INSULATION:
- Our Optimal insulation is 100% natural
- Irritant free, it is easy to install and offers excellent heat and acoustic insulating properties.
- Our Optimal insulation absorbs moisture, helping it regulate humidity in the roof space.
- Optimal insulation has a density of 18 kg/m3
- Available in widths of 380mm or 570mm to suit the distance between the joists in your loft
- Available in thicknesses of 50mm or 75mm.
HOW TO CALCULATE HOW MUCH YOU NEED:
Using the thermal conductivity of this product (0.0385), you can work out either the thickness you require or the U-Value you will achieve. Simply divide the thermal conductivity by the thickness to work out the U-Value, or divide it by the U-value you want to reach to work out the thickness required.