Techniques
We as architects are often way too into buildings (seven years at university tends to do that). So we refer to a lot of technical jargon like its second nature. Bringing on some new trainees has taught us that what we say isn’t always as straightforward as we think so we put this page together to show you some of the key elements of building construction that we use.
Each of our projects that uses one of these services will be marked with the corresponding icon so you can see the finished product at a glance.
SIPs
Sip or Sips panels are structurally insulated panels. They make up the walls and exterior faces of a building. They are a more eco-friendly construction method due to the reduced waste and high thermal insulation they provide. Sips are manufactured offsite to the precise specifications. The core of these panels is injected Zero ODP rigid insulation which is sandwiched between two Oriented Strand Boards (OBS). This makes the panels highly thermally efficient and airtight which gives it minimal thermal bridging.
Sips are a good solution for challenging rural locations where access is limited because of steep or narrow lanes. The off site fabricated sips require far fewer deliveries than traditional methods so can be taken to the site more efficiently. This adds to it’s sustainability by reducing the fuel consumption and impact on the local surroundings. Sips are designed to fit together so teams trained in assembling sips systems can assemble them quickly and efficiently. Size dependent, sips projects can be assembled within a month to provide a watertight frame ready for internal and cladding work.
The panels can be used for external cavity walls, separating walls, internal load bearing walls, and flat or pitched roofs. This is because they have strength similar to brick walls and if sealed together correctly limit the risk of condensation and interstitial condensation. The fire resistance of SIP external walls is provided by the wall linings. These wall linings are typically plasterboard, although other types of fire resistant board could also be used. Typically, one layer of 15mm plasterboard fixed to timber battens will provide 30 minutes fire resistance to a SIP wall.
Brick & Block w/ insulated Cavity
Brick or block walls are the most common walls in the United Kingdom and haven’t changed substantially since their use became widespread in the 1920’s. There is an element of flexibility with this style of construction. We tend to build the internal leaf from aggregate concrete blocks or from aircrete blocks and we can insulate the cavity with either half fill or full fill insulation. Aggregate concrete blocks are made of crushed rock and are denser than aircrete blocks which are made of a finer crushed material. Both bricks come in a variety of sizes and strengths offering different structural and thermal performance properties to suit specific project needs.
The insulation we use is either PIR or PUR, rigid boards made of polyisocyanurate or polyurethane respectively. They are constructed by blowing gas through the chemicals to form rigid, low density blocks. Both the chemicals and the gas have a very low thermal conductivity. The closed cell gas bubbles and aluminium foil bonding help to form a vapour barrier that makes it a suitable material for roof or floor insulation.
Phenolic panels are very similar and can be used should a project require it. They’re another rigid insulation board made out of high density thermo-setting cellulose fabrics along with phenolic resins. They also have a closed cell structure so they are vapour resistant however they have a higher r-value giving them greater insulation and a thinner profile.
Retrofit Insulation
When performing renovations to properties we can perform some tasks to make them more thermally efficient. Retrofit insulation comes under this. This method can be applied internally or externally. External Insulation is used more frequently as it doesn’t reduce the internal floor area. It often takes the form of insulated render that is applied to the brickwork of a building. If render is already applied it is removed prior to insulation to avoid problems.
Internal insulation is often retrofitted to buildings with poor thermal efficiency where the external walls can’t be altered. This could be because the building is within a conservation area, an Area of Outstanding Natural Beauty (AONB), or is a listed building. This insulation makes use of rigid insulation backed plasterboard fitted with an internal vapour membrane and secured to the wall by timber battens to allow moisture to be evaporated away.
Both forms of retrofit insulation reduce heating bills. External insulation does this by altering the thermal mass of the house while internal insulation simply reduces the thermal transmittance of the building. External insulation has the added difficulty of having to alter windows as the depth of the walls changes. This can be justified by the increase to the life of the wall and the reduction of condensation or damp on internal walls where this is a problem.
Mechanical Ventilation with Heat Recovery
Mechanical Ventilation with Heat Recovery is a system to ensure good air quality within a structure. In low energy buildings we want all air movement to be intentional. Practically this means we want our designs to be airtight to stop cold air from infiltrating the building and causing draughts which would increase the heating costs. With an MVHR system air enters the building through a vent and passes through a heat exchanger before being introduced to the rooms. The air then circulates through the rooms until it reaches extractors that collect the now stale air and direct it outside through the other side of the heat exchanger.
This keeps any energy spent heating the building inside the building.
MVHR can also solve problems a structure has with damp. Damp occurs when walls are made airtight and moisture doesn’t have a way to escape or where in breathable buildings the thermal insulation is poor which puts the dew point on the internal surface of a wall rather than in the wall cavity where it can evaporate. MVHR removes moist air from inside the building and replaces it with air taken from outside which has a lower moisture content. This kind of ventilation is applied to the whole property so additional moisture extraction systems like shower ventilation and overhead cooker extractors aren’t required.
MVHR systems aren’t always the correct choice for a property. These systems require ducts to run through the building. The route of these ducts is important as it affects the efficiency of the system so layouts of rooms can be influenced by the requirements of the system.
Natural light
It’s obvious that structures should have access to natural light. It is beneficial for your health and well being; a good source of Vitamin D; required by plants; and important for regulating the body clock not to mention ephemeral features like making an environment more comfortable and improving concentration.
Projects marked with this symbol make use of passive light solutions to collect and direct natural light so that it is more equally distributed across the structure. For maximum daylighting and possible passive solar heating we can install a skylight. The effect these give varies greatly on the orientation. Skylights on north-facing roofs provide a fairly constant amount of natural light; east-facing roofs provide light and heat in the morning while west-facing roofs provide afternoon sunlight and heat; and south-facing roofs provide the greatest potential in the winter but often get too hot in the summer.
For rooms where skylights would be intrusive or unfeasible sun pipes can be installed. These thin reflective pipes collect light and diffuse it in a room through a fitting similar to a regular light fitting. They can go through attic spaces and can be installed on south facing roofs without the unwanted solar heat gain. While the domed versions of these systems stand out less intrusive conservation rooflights can be used to avoid altering the look of a building. Sun pipes often don’t need to disturb the rafters of a building.
Other solutions include installing clear doors to allow light to diffuse into corridors with no external windows and in taller buildings light shelves are popular for redirecting light entering a room at a steep angle.
Passive ventilation
Passive ventilation describes ventilating your home using only natural forces. In its simplest incarnation this would mean opening windows to let stale or humid air out and fresh air in. Most passive systems however rely on vents to circulate air. They require no power source to operate and while this uses less energy it is balanced out by the increases in the energy used for heating. Primarily these systems deal with humidity and condensation and small systems can be installed on a room by room basis.
Full structure ventilation this way can have some advantages over mechanical ventilation systems but the large ducts required to utilise this system make it very situational to retrofit. This isn’t a problem for new builds that are designed to include space for the passive ventilation systems but it is still difficult to control the movement of the air.
Humidity sensing Intelligent Passive Stack Ventilation can be used to limit the ventilation and heat loss from a building. This with a heat recovery system would minimize your heating costs and only slightly increase your power usage but is quite complicated and expensive to install. It begins to become clear that this type of ventilation is a very difficult balancing act and isn’t suitable for every project.
Grid
Most buildings in the uk are connected to the national electricity generation and supply network. The national grid runs on large scale centralised Alternating Current (AC) generation done by gas, nuclear and wind power stations. These are located away from centres of population and require stepped up transmission for electrical efficiency. This kind of electricity requires stepping down before usage. This is done by transformers located in electrical substations.
To arrange for a new electricity connection for a self build home or for a temporary supply while building, you need to contact a Distribution Network Operator (DNO) for the connection and an ‘energy supplier’ to arrange a meter. A temporary supply requires a temporary secure, watertight powerbox to hold the meter tails, consumer unit, and power point. Once this is installed it can be re-routed once building is complete. If a property already has power and the new build is within the boundaries of the property power can be re-routed and submetered without involving a DNO.
Space heating
Arkhi tends to offer either traditional radiators or underfloor heating for space heating. Your choice will determine how heat is distributed around your property. Radiators work by heating the air around them first. This hot air travels up and away from the radiator drawing colder air from elsewhere to fill the gap behind it. This will heat an entire building but can cause hot and cold spots to form. Underfloor heating maintains a fairly consistent temperature at floor level that slowly rises, displacing the cold air above it which sinks down to where it can be heated by the system. Underfloor heating doesn’t create the traditional air currents or cold spots that a radiator does.
Underfloor heating is most effective for a ground floor as it can be encased in concrete to increase the thermal mass of a building to buffer heat losses and gains. It can also be applied to above ground floors through the use of pipes installed under the traditional timber deck but it isn’t suitable for every property. In most projects it's up to the clients to determine the correct space heating solution for them. Underfloor heating installed in zones benefits from the same ability of radiators to warm up specific rooms although the effect they will have will be less immediate than those systems.
Radiators present the cheaper option when installing space heating however they are installed within the building footprint which reduces the internal square footage of the building.
Photovoltaic
By now photovoltaics are a well known way to decrease your carbon emissions and reduce your energy costs. Despite advancements in the technology they still require a large upfront cost. Photovoltaic Solar panels are installed onto a mounting structure that is secured to the roof rafters. This creates a 20 to 36 degrees angle for the panels that will allow them to maximize their sunlight collection. Similarly they’re most effective on south facing roofs with little shade. The panels are attached to the mounts and wired behind to minimize exposure for the cables. Once wired together the photovoltaic grid can be connected to a battery to store the charge or straight to an inverter that transforms the energy into a usable power source. This is fed to the building by a consumer unit installed in or by the fusebox.
One of the benefits of solar panel installation is that it is classified as permitted development. Planning permission will only be required for buildings in conservation zones, listed buildings, or areas of outstanding natural beauty. Solar panels require very little maintenance. They do require cleaning. Different installers have different requirements as part of their warranty and some require you to use professional cleaning services.
Wind
Wind power isn’t a very popular form of renewable energy. It is loud so they’re often only considered on rural sites with space for the large construction. I’ve never disliked the look of the traditional wind turbine but to some Local Planning Authorities it is considered a disruption to the local development plan so planning permission can be difficult to acquire. It is possible to install wind turbines under permitted development rights with specified limits and conditions.
Not all sites are suitable for wind power. Open rural areas or coastal areas have the most reliable wind and turbines here produce the best results. Wind turbines aren’t allowed within a conservation area or an Area of Outstanding Natural Beauty (AONB) because they can affect the local ecology of an area.
Despite these concerns wind power is quite cost effective.
Air Source Heat Pump
An Air Source Heat Pump (ASHP) is a heating system that doesn’t use fuel or convert electricity into heat. It absorbs heat from outside the building through a network of tubes filled with refrigerant. This is compressed to increase the heat and fed into a heat exchanger. The heat is then distributed by the building's central heating and hot water. These heat pumps even work if the temperature is below zero.
These heating systems are extremely sustainable. They produce zero carbon emissions and provide cooling in summer as well as heating in winter. They are a good match for underfloor heating systems because they have a lower output. A larger surface area for heat transfer means you require a lower temperature to transfer the same amount of heat. This also means the heating is more gradual. Using a radiator system is viable but often requires replacing the existing radiators with larger models. While they are a great source of hot water the water will be cooler than from a boiler. Buildings solely using ASHP’s may need a larger hot water tank to cover their needs.
ASHP’s can be separated into Monobloc or Split systems. Monobloc’s have to be installed close to the building to stop heat loss. Split systems have a separate compressor unit inside the building and therefore don’t suffer the same heat loss and the condenser can be installed up to 30m away from the building. This is useful as the condenser can produce a lot of noise. This is not a concern during the daytime but running this form of heating at night in rural sites requires the condenser to work a lot harder to produce the same level of heat.
Ground Source Heat Pump
A Ground Source Heat Pump (GSHP) is a heating system that doesn’t use fuel or convert electricity into heat. It absorbs heat from underground through a network of pipes called a ground loop. These are filled with a mixture of water and anti-freeze. The liquid is fed through a compressor to increase the heat then a heat exchanger, which extracts the heat and transfers it to the heat pump. This then transfers the heat to your central heating system.
These heating systems are extremely sustainable. They produce zero carbon emissions and provide cooling in summer as well as heating in winter. They are a good match for underfloor heating systems because they have a lower output. A larger surface area for heat transfer means you require a lower temperature to transfer the same amount of heat. This also means the heating is more gradual. Using a radiator system is viable but often requires replacing the existing radiators with larger models. While they are a great source of hot water the water will be cooler than from a boiler. Buildings solely using GSHP’s may need a larger hot water tank to cover their needs.
GSHP are more efficient than Air Source Heat Pumps due to the higher average temperature of the ground. They are installed either in a horizontal trench or a vertical borehole. The horizontal method is cheaper to accomplish as it is closer to the surface but it demarcates an area that can’t be developed or planted on, typically this is used as a garden. A borehole is deeper and while it has an increased cost associated with it, it benefits from a higher ground temperature. It enhances the performance of the system and its heat output.
Immersion Heater
An Immersion Heater is an electric heating system that uses a large heating coil submerged in a water tank to provide hot water to a building. It can be used as the primary source of hot water or as a combination with another heating system. While hybrids are the most common way of utilizing immersion heaters, some rural or new buildings make use of them as the sole provider of hot water as they don’t require a connection to the gas network.
The combi boiler would be separated from the building's central heating. This means if your central heating breaks down you still have a supply of hot water to hand. The cost of running an immersion boiler can be high for family homes. To provide hot water the entire tank needs to be heated even if a small amount of water is needed. This is why it’s recommended that boilers fitted with an immersion heater be fitted with insulation to increase the amount of time the water remains hot after heating. If insulated an immersion boiler can be programmed to turn on and off at certain times to maintain the temperature of the water so you don’t need to leave it on and waste time. If you run out of hot water and the programmed time for the heater isn’t for several hours they are easy to turn on manually to boost your hot water supply. Because they use electricity they can be set to heat water during off peak hours when electricity is less expensive to lower the cost. Immersion heaters can be used in tandem with renewable energy sources to lower the carbon emissions of a building.
Solar thermal
A solar thermal heating system works very similar to solar panels. The solar thermal panels are attached to a mounting structure that is fastened to the rafters. These panels collect heat which is transported by fluid pipe and transferred to the building's central heating system by a heat exchanger. They are used in conjunction with another form of heating.
There are two types of solar thermal panels to choose from; flat plate collectors or evacuated tube collectors. Flat plate collectors are flat panels with a dark glazed surface similar to PV panels. Underneath the plate are copper or aluminium tubes filled with the fluid used to transport the heat. The evacuated tubes look like a series of glass tubes in a parallel row. They make use of vacuum insulation to increase the efficiency of the system. As with most renewable energy sources solar thermal is inconstant. A solar thermal system can produce between 40-70% of the water needs for a family of four. They are most effective on south facing roofs with little shade. Systems have a typical life expectancy of 25 years and will function automatically with minimal maintenance.
Biomass Boiler
A biomass boiler is a combustion heating system that uses natural resources as a fuel. There are three main types of biomass boilers; wood pellet, wood chip, and wood log boilers. They work on the same principle as gas boilers but are eco-friendly and sustainable . This makes using a biomass boiler easier as it works much like the existing boiler with the exception of being fed fuel. This can be done automatically or manually depending on the fuel and make of the boiler. Maintenance on this type of boiler involves removing ash that accumulates from the fuel.
The wood chip fuel is made of off cuts from the production of other wood products. This makes it cheap, sustainable, and readily available. Wood chip boilers will often take up the most room to install but have less storage requirements than log boilers. The wood pellet fuel is recycled from sawdust. This fuel is better suited to use in an automated hopper than wood chips because of the standardized size. The fuel burns for a longer time than the wood chips so you require less of them saving on storage space. Fueling a boiler with wood logs can only be done by hand. This type of boiler doesn’t require as much space as the wood chip boiler but has a greater demand for storage space.
This type of central heating can be used alongside a gas boiler, with another renewable energy source, or as the sole provider of hot water. It is a reliable source of heating and provides heat throughout the winter with little fall off. The cost of installing a biomass boiler will be higher than gas but unlike gas the price of the fuel is low and isn’t expected to increase in the future. Using this can also make you eligible for financial backing through government schemes like the Renewable Heating Initiative (RHI).
Gas Boiler
A gas boiler is the standard for central heating and hot water. The boiler burns gas to heat water that is pumped around the building in a circuit. A gas burner also heats the hot water produced by taps through a heat exchanger that transfers the heat to the water supply. Heat only boilers use a separate circuit for water used for taps while combi boilers directly affect the incoming water supply. The largest difference between these types of boilers is that heat only boilers require an extra tank to store the hot water for taps. This gives them a bigger buffer on the amount of hot water that can be used at one point.
Gas boilers are usually replaced every 15-20 years due to drop offs in efficiency experienced by these systems as they age. Depending on the make of the boiler they are between 70%-90% efficient. If a property is connected to the existing gas network it makes it easier to install a gas boiler but it is possible to run a gas boiler off bottled gas. This requires a little more involvement in changing the bottles and a place to store them but is a viable option for remote locations.