Our Technical Specification & Unique Urban Marque System
Modern methods of Construction (MMC) have brought us many new and innovative ideas and ecology plays a great part in this construction industry revolution (click here to see our Ecology Statement).
Our Urban Plinth System illustrates this point perfectly and has been used on several different types of structures to replace concrete foundations. The Urban Plinth System is a fully tested and bespoke engineered solution that can be used on uneven ground, difficult terrain, tight sites and in flood protection plans, as well as being a cost effective and time saving option as they can be installed quickly and without fuss or mess in most locations.
Benefits of the Urban Plinth System
The Urban Plinth system is a fully engineered foundation system and specific installation plans are supplied for each individual Mobile Home and Static Caravan. Can be used for bespoke designer Lodge Homes and Caravan Units as well as all other Log Cabins, Annexes and Park Homes. All plinth locations are bespoke engineered to your specific lodge design and metrological data at the specific site location, which takes into account the wind, rain and snow loads in your area. Loadings are certified by our fully insured & chartered structural engineers for your peace of mind.
Our mobile homes must be raised off the ground, so that we can slide steels under the unit to lift it in order to comply with the Caravan Acts – it also helps it to breathe, as there is an airflow under the floor cassette and has an added benefit to your insulation calculations. The other benefits of a raised caravan is that it reduces pest access to the unit, flood and splash-back doesn’t affect the structure and you are not relying on a damp proof course (DPC) to isolate the structure from ground water and rising earth salts.
There are alternative methods available for foundations to either meet building regulations or alternatives that may have been specified by a different chartered structural engineer or architect. We are happy to work with client’s architects or engineers, however if planning permission has been obtained, the local building control need proof that they are fit for purpose.
How to decide on a foundation mainly depends on the loads that the proposed building will impose on it. This is a very complicated subject and engineers need to calculate and specify this on a design-by-design basis. A unit in the Highlands of Scotland will act differently to one installed in the flat Fenlands of Cambridgeshire. All designs and calculations required to meet UK Building Regulations are part of the “complete structural timber frame package” supplied by Urban Marque Ltd.
AT ALL TIMES THE CLIENT IS RESPONSIBLE FOR THE GROUND WORKS & CONDITIONS Urban Marque Ltd do not undertake any ground-works or guarantee soil/land conditions – therefore cannot be held responsible for the work of others.
Vapour Barriers
This is quite a technical subject, and rarely mentioned by most suppliers of Mobile Homes and Static Caravan suppliers as they simply don’t install them! The fundamental problem caused by the absence of an insulation vapour barrier in any timber frame building can lead to serious damp problems.
When you apply internal insulation to a wall or roof space it creates a ‘warm side’ and a ‘cold side’ where the exterior wall or outside of the roof insulation becomes colder (for the 11 months of non-summer in the UK). This creates a danger that vapour from inside the home created by showers, washing machines, electric kettles and human breathing will get through the plasterboard, behind the insulation, and as it cools will condense on and inside the wall fabric in the same way that you get condensation on the surface of single glazed windows.
To prevent interstitial condensation the internal airborne vapour must be prevented from percolating through the walls, cooling and then turning into liquid. This is particularly important, to prevent wet or dry rot, in timber frame construction and where timber battens are attached to the wall to secure the insulation. The better your insulation the colder the wall behind will be, so the more important it is to prevent excessive moisture entering it.
So what is a vapour barrier? It is a very simple component like a large sheet of specially manufactured polythene (type) film that is simply tacked onto the timber studs and then taped on the joints to make 100% sure that no moisture laden air can find a way through it. At this stage it is crucial that any holes in the membrane caused by cables or pipes that have to be pulled though must be sealed with appropriate tapes to ensure a complete air-tight barrier.
Many modern insulations such as Urban Marque Ltd Superfoil + multi chamber insulation installed with auxiliary components will have its own built in vapour barrier so there is no need to struggle with huge areas of plastic sheeting that has a mind of its own! Urban Marque Ltd will always specify the correct combination of product for your new Mobile Lodge Home or Garden Annexe.
Insulation
Insulation is a complicated but essential consideration in both traditional house building and high-end mobile homes and static caravans. Even log cabins and garden annexes need good quality insulations to achieve a good U value See thermal values on our website here. Not only does it have to conform to many compulsory building codes, it has an important role to play in both ecological and whole-life costs of your home.
Good quality insulation, correctly specified by you supplier keeps your home warmer in winter, it also helps keep it cooler in summer. We call this the “Thermos Flask” effect. Air is a poor conductor of heat, so that any pockets of air trapped in insulation minimise the amount of heat which can pass between the inside and outside of your house. This means that in winter, the heat stays inside a home and in the summer it stays outside! Different types of insulation materials have different properties, so are suitable for different areas of a building.
The general opinion of ‘the thicker the insulation the better’ is a myth! As an example a modern product such as a Multifoil of 22mm can supply a lower U value that 100mm of a market leading PIR sheet or 200mm of a Rockwool product.
Room temperature in a dwelling is all about balance, to keep it at the required level for as long as possible, without requiring mechanical assistance to boost or reduce. This can be affected by the type of construction, insulation choice, family habits and heating type etc. Warm air seeks a cooler location so it’s essential to keep the space balanced for maximum efficiency, lower carbon emissions and of course heating costs.
Modern Methods of Construction and Government demands mean that insulation products have hugely improved from the old fashioned methods and nowadays the technical properties and performances can be guaranteed. The best advice for choosing insulation is get the best you can afford even if it means borrowing a bit of the budget from elsewhere. We use a combination of products that produce a market leading U value at excellent value for money.
What are your Alternative Options for Insulation?
Remember that target values are measured in U values and the lower the achieved U value the better the heat retention is and the lower the carbon emissions are.
We get asked a lot of questions on alternative insulations by self build clients who wish to undertake this part of the installation themselves. There are many new-wave supposed eco-solutions such as shredded plastic bottles and newspaper etc but remember that we have to meet very high standards of U value efficiency under the UK Building Regulations and Eurocodes which are expressed as W/m2K and we have to produce thermal calculations to prove that we have met the proscribed U values. As an example a wall U value requirement may be expressed as 0.22 W/m2K and we have to achieve this by specifying a material or selection of components that combined will give us the demand U value. If we up-rate the combination or increase the insulation the U value will lower (unlike R values that will rise). Using “alternative” insulation materials can often cause complication with the calculations—so we advise to stick to known commercial products. Alternatives that self-builders may wish to consider if undertaking this scope of works themselves:
Sheep’s wool
Sheep’s wool insulation is a fairly new insulation product, however before it is used as an insulation material, it must undergo an intensive cleaning process in order to remove the dirt and oils from the wool. The chemicals and energy used during this process must be taken into account when measuring its environmental impact. Like most ecological products It is not a cheap option!
Glass mineral wool (glasswool)
Used to be the world’s most popular and widely used insulation material, glasswool is made from recycled glass bottles, so it is ultra-eco-friendly. It is easy to handle and install, it used to be the most cost-effective insulation available but it has increased considerably in price recently and is now almost the same price as other solutions. The most popular brand names for this type of product are Rockwool and Isover.
Rock mineral wool (Mineral Wool)
Rock mineral wool has a more solid structure, so is ideal for situations where it may be under compression, (e.g. on a flat roof).
Mineral wool insulation products are available in rolls of different widths and thicknesses for quick and simple DIY installation – for example, between the rafters in a roof or joists in a ceiling or floor. It can also be produced as lightweight ‘slabs’ for installing into the cavity walls when building new houses. ‘Loose’ mineral wool can also be used to fill cavity walls and is blown in through a hole drilled in the wall after it is built.
Installing mineral wool insulation is also an effective fire safety measure, as it does not burn easily, so can prevent fire spreading. In fact, rock mineral wool can resist temperatures above 1,000°C. The most popular brand names for this type of product are Rockwool and Isover.
Rigid Foam
Rigid polyurethane (PUR) and polyisocyanurate (PIR) insulation products are highly effective, lightweight and many have the ability to bond to most materials. Their excellent thermal conductivity and high strength to weight ratio, combined with great manufacturing versatility provides a range of products. As a result, PIR/PUR insulation products are a popular choice for most construction insulation applications. Rigid foam insulation has high compressive strength and is used where it needs to support weight (e.g. under a floor, or in lofts as a storage solution). Standard panels supplied are not fire resistant and need to be installed in conjunction with other barrier products that are. As well as strength and durability, some rigid foam insulation can also provide additional properties such as fire resistance and acoustic insulation but these are quite a expensive solution. The most popular brand names for this type of product are Celotex and Kingspan.
Modern Foils (Hybrid)
This is the new kid on the block and is without doubt the best choice in terms of performance and cost. Foils are a reflective insulation product based on a honeycomb structure made of shaped polyethylene foams glued to aluminium coated polyethylene foils. High thermal performance is provided by a special structure composed of a large number of low emissivity cavities, protected from dust and excessive air movement. Moreover, the low emissivity external films provide additional thermal resistance, when associated with air cavities. Products are available in a range of thicknesses and each of these hybrid products combine to meet insulation, air tightness, moisture resistance demands and also have reflective properties.
Modern Hybrid insulations can also meet the UK and Euro fire class requirements quite easily and economically. Another added benefit to using this type of product is that it can be used with any other inexpensive insulations and barriers to achieve any level thermal U value demanded under any building code.
Care must be taken when specifying all types of insulation combinations and a thermal calculation should be run to guarantee compliance levels.
When you buy an Urban Marque Ltd mobile home, granny annex, or log cabin we will guarantee the U values achieved by issuing you with a thermal compliance certificate.
What are Thermal Values?
All new buildings must meet an overall thermal level so walls floors and ceilings need to be designed to meet the minimum requirements laid down by construction rules. By adding insulations and barriers, the minimum levels can be improved. Normally, the thicker the component is the better – but this is not the case with insulation. With modern materials a 40mm thick insulation can contribute to a much lower U-value than a 200mm thick wool product could! Urban Marque Ltd spend a great deal of time identifying and testing new products so we are always at the cutting edge and able to provide thermal calculations to our clients to prove that our choice of materials and components will meet their specified demand.
So what is a U-Value?
U-value is a measure of how much heat will pass through a thermal object, like a wall or window. A low U-value means little heat will pass through it. U-value is measured in W/m2K – that is, Watts per square metre per degree Kelvin (1 degree Kelvin is the same as 1 degree Centigrade, but with a different zero).
So if a wall has a U-value of 1.0, then 1 m2 of wall will let 1 Watt pass through it when there is a temperature difference of 1 degree between the inside and outside.
Typical limits of U-value in buildings vary from a maximum of about 5.0 W/m2K for a single-glazed window to a
minimum of about 0.15 W/m2K for a modern roof with 300mm of loft insulation – so the window lets about 30 times as much heat pass through 1m2 of it, compared to the roof.
K-Value
The wall is called a ‘thermal object’ above because its U-value can be calculated from each of the components it is made of.
Each component, say the outer skin of brickwork in a cavity wall, will let heat pass through it based on two factors:
1. Its thermal conductivity
2. How thick it is
Thickness matters because in general the thicker something is, the slower heat will pass through it – a thick jumper keeps heat in better than a thin jumper.
The thermal conductivity is a measure of how easily heat passes through the material and is called the k-value (little ‘k’ which helps stop confusing it with big ‘K’ degrees Kelvin!). k-value is measured in W/mK. Thermal conductivity is an inherent property of a material, like stiffness or density.
The U-value of a single component is given by the formula U = k / l, conductivity divided by thickness (in thermal calcs the thickness always seems to be represented by ‘l’, not ‘t’ as you might expect).
So that outer skin of brickwork, on its own, might have a thermal conductivity, k of 0.84 W/mK and a thickness of 100mm (or 0.10m), so U = 0.84/0.10 = 8.4 W/m2K – yes, worse than a single-glazed window!
Typical limits of k-value in building materials are a maximum of around 2.0 W/mK for concrete and sandstone to a minimum of about 0.025 W/mK for modern insulation materials.
R-Value
– You will come across this in UK evaluations, so it’s worth mentioning.
America uses a different way of expressing resistance to heat flow, using the R-value, thermal resistance. This is just the inverse of the U-value, so 1/ R = U. Of course they don’t use metric units, so you can’t compare their R-values directly with ours.
So big R-values are more resistant to heat flow. In (European) SI units a U-value of 0.2 will have an R-value of 5.0 m2K/W and this would be equivalent to an American R-value of 28 (units are h.ft.ºF/Btu) – American R-values are 5.67 times SI R-values.
We have to use R-values in thermal calculations because we can’t add up the U-values of each component in a thermal object – but we can add up each component’s r-value to get the total R-value (little ‘r’ is used for the components and big ‘R’ is used for the whole thermal object).
So R = r1 + r2 + r3 + r4 and so on. Each individual r is the inverse of the u-value, so r = l / k, thickness divided by conductivity.
Exterior Cladding
Exterior cladding is a sacrificial protective layer of materials that separates a building’s structure and interior from exterior elements, such as weather and sound. The exterior cladding is often not one material but an assembly of materials, and each material has its own importance in blocking exterior conditions. The external ‘skin’ of a building isn’t a load-bearing element so its main purpose is to act as a raincoat for the structural elements and to look ‘nice’ !
Water
Water is often considered the hardest element to defend against on a structure. Moisture is repelled using quarry products such as brick, block or stone, timber or composite cladding, waterproof membranes, weeps, sealant, weather- striping and flashing. The cladding or external finish is the first line of defence and is usually the most important element. The membrane, sealant, flashing, etc., protect the structure from any moisture that penetrates the outer protective coat..
Temperature
Exterior cladding protects a structure from temperature extremes and variations by isolating the interior from the exterior along with a cavity and insulation. Rigid insulation, built-up layers of material, and double-glazing protect the interior from exterior temperatures by creating thermal gaps that do not allow the temperatures to be conducted through the cladding, bridging exterior temperatures to interior temperatures.
Wind
The building’s structure and interior are shielded from the wind by the exterior cladding. To avoid damage to the cladding, the materials are redundantly and securely fastened to the structure, while allowing minimal movement by the wind. The method of fastening the cladding to the structure is especially important in areas with high winds and cladding must always be considered in the site-specific *structural calculations and thermal design of the subject building.
Solar Damage
Exterior cladding deters damage and deterioration from the sun and ultraviolet waves. A structure’s exterior elements must be able to resist the harmful effects of the sun. Otherwise, the failing material will provide access to the interior for moisture and temperature. Many plastic and wood products are not appropriate for exterior cladding be- cause they can degrade quickly when exposed to the sun.
Innovative Cladding Systems
Many contemporary cladding systems are novel and provide protection from the exterior with a thin skin. Modern systems such as aluminium and glass architectural glazing can insulate and shade a building as well as traditional masonry and wood systems. Other cladding systems are similar to screens, able to filter out the wind and sun, but allowing air to flow through the structure’s skin. Eco products are not always suitable as grading, drying and preserving may not be possible. Many new systems require specialist installation and can be very expensive in the long-run.
*Structural Calculations Are a structural engineers in depth investigation & report of all the components that are to be used in or on a building and also the historic weather patterns on the specific site that will affect loadings
Timber cladding provides a highly attractive and durable external finish which is a wholly ecological choice as it is renewable, reusable, biodegradable and requires minimal embodied energy from forest to site. For years we have used different types of timber for cladding buildings with different results and life-spans The most economical option is an imported sustainable Redwood that has been grown in a cold climate, harvested from managed plantations and sent to the end user on a certified chain of custody such as FSC approved. It is however imperative that any timbers are treated with a water-born vacuum impregnated preservative prior to use. (Copper based preservatives and Creosote are no longer an acceptable method of preserving external timbers that do not have ground contact.
Other popular cladding timbers are Larch and Western Red Cedar both of which have a longer lifespan that Redwood but are around 40% more expensive. Today in an age where we are all ecologically aware of the irreparable damage to forests new technology has enabled us to supply sustainable softwoods that have been modified to raise them to the same durability level as Mahogany and Oak but at a fraction of the cost.
ThermoWood has become a very popular choice for many external applications which starts life as Pine/Spruce/Fir. ThermoWood® is produced by heat treating Finnish grown pine and spruce to temperatures in excess of 200 degrees centigrade. During the heat treatment, chemical and structural changes occur within the timber which alter and improve some of its basic characteristics. The resulting product is an altogether more durable and stable timber, an ideal cladding material for use in exposed areas such as external walls.The finished colour of ThermoWood-D (pine) is affected by the treatment temperature and time. The higher the temperature the darker the appearance.
Accoya Accoya® wood also starts life as a sustainable softwood and undergoes an acid modification process from the surface to the core and has measurable consistency throughout. The result is a durable, stable and beautiful material that won’t rot, twist, warp or shrink. Think of Accoya wood as having the performance characteristics of the most durable tropical hardwoods.
Iroko Ipe & Garapa Etc South America & Africa supply a host of very dense hardwood timbers that are extremely durable and will provide a long life. You should be sure that these timbers have entered the UK legally and have been certified for sale by the exporting governments.
Composite Fibre and UPVC are an alternative to timber and many are supplied in a range of colours and finishes. They can be expensive if they require specialist installation but are usually maintenance free. Profiles Most of the above are available in different profiles such as Shiplap, Waney & Featheredge, T & G & Half-log. The machine finish sizes vary but the minimum sizes should not be less than 19mm thick x 119mm wide. It is more economical to buy a profile and grade from a merchants stock although most will machine a batch with the profile of your choice