| passive solar gain | designing for energy efficiency begins early in the planning process. a layout which takes advantage of natural heat and light from the sun (known as "passive solar gain") and uses air movement for ventilation can reduce the need for artificial light, heat, cooling and ventilation. |
| particulate | tiny pieces of solid or liquid matter, such as soot, dust, fumes, or mist. |
| passiv haus | a very energy efficient building standard used across europe. for 40o - 60o northern latitudes, a dwelling is deemed to satisfy the passivhaus criteria if: the total energy demand for space heating and cooling is less than 15 kwh/m2/yr treated floor area; the total primary energy use for all appliances, domestic hot water and space heating and cooling is less than 120 kwh/m2/yr |
| passive solar design | the principle of passive solar design is to optimise the amount of energy that can be derived from the sun. this can be achieved through the careful design and orientation of a building or a whole development. |
| passive solar design | the principle of passive solar design is to optimise the amount of energy that can be derived from the sun. this can be achieved through the careful design and orientation of a building or a whole development. |
| passive solar gain | designing for energy efficiency begins early in the planning process. a layout which takes advantage of natural heat and light from the sun (known as "passive solar gain") and uses air movement for ventilation can reduce the need for artificial light, heat, cooling and ventilation. |
| passive solar heating | using the sun's energy (in the form of heat) to diminish a building's heating load, usually through the use of large window areas which permit light penetration upon some massive material to utilise the material's thermal storage capacity. |
| passive system | a system of heating and cooling buildings by natural energy sources without electrical or mechanical assistance. |
| payback period | the period it takes for the stream of net cash flows to equal the initial investment. for renewable energy systems, it can also be used to refer to the period of time over which energy cost savings derived from accessing renewable energy, offset the up-front capital costs of the system. |
| perlite | expanded volcanic glass, very light in weight and useful as insulation although it is not as effective as some materials. can be added to plaster and is fire resistant. |
| permeability | a measure of the ease with which a fluid can flow through a porous medium. it depends on the physical properties of the medium, for example grain size, porosity and pore shape. |
| permeable surface | a surface formed of material that is itself impervious to water but, by virtue of voids formed through the surface, allows infiltration of water to the sub-base through the pattern of voids, eg concrete block paving. |
| permeable surfacing | materials such as porous concrete blocks, crushed stone/gravel or porous asphalt can be used to encourage surface water to permeate into the ground. depending on the ground conditions, the water may infiltrate directly into the subsoil, or be stored in an underground reservoir (e.g. a crushed stone layer) before slowly soaking into the ground. |
| permeable surfacing | materials such as porous concrete blocks, crushed stone/gravel or porous asphalt can be used to encourage surface water to permeate into the ground. depending on the ground conditions, the water may infiltrate directly into the subsoil, or be stored in an underground reservoir (e.g. a crushed stone layer) before slowly soaking into the ground. |
| persistant organic pollutant | a complex organic chemical which resists decomposition in the environment and can migrate over great distances, which bio accumulates and biomagnifies, and which is suspected of being toxic to humans or other organisms exposed to even low concentrations if such exposure occurs over a long period of time. |
| pervious surface | a surface that allows inflow of rainwater into the underlying construction or soil. |
| phenols | hydrocarbons used to make resins and glues. very toxic and may outgas |
| photovoltaic (solar) cell | generally speaking, a device incorporating a semiconductor that generates electricity when exposed to sunlight (or any other form of white light). the technology may be further sub-divided into crystalline, multi-crystalline, thin-film and concentrator variants. |
| planning permission | planning permission from the local planning authority is required for most forms of what is called development. some changes or additions to property are classified as "permitted development " and don't normally need planning permission.. some changes of use are also classed as development and require permission. if you build something without getting permission you might have to remove it. if you do need permission you will need to apply for it to the local council. you will need to fill in an application form, provide drawings and a site plan and pay a fee. outline planning permission (opp) this gives an outline of the permitted development, such as the size and height of the building. full details of the building must be provided and approved before building work can start. detailed planning permission (dpp) : approval of reserved matters land with outline planning permission must obtain detailed planning permission before the building works can start. full planning permission (fpp) full planning permission is when outline and detailed planning permission are requested at once. building must then start within five years. |
| polyethylene | a semi-transparent plastic used in sheets as vapor barriers or for packaging and containers; made in high density (hdpe) and low density (ldpe) varieties. low in toxicity, it produces low risk vapours when burned. |
| polyethylene terephthalate (pet) | polyester resin used in the manufacture of polyester fibers and sheet plastics such as recyclable soft drink bottles. |
| ponds and wetlands | these can be particularly beneficial during heavy rain due to their capacity to hold large amounts of water and therefore reduce flood risk and are best suited to larger sites where they can be incorporated into landscaping schemes. ponds and wetlands also help with grit removal. algae and plants in wetlands can significantly assist with filtering and nutrient removal. |
| ponds and wetlands | these can be particularly beneficial during heavy rain due to their capacity to hold large amounts of water and therefore reduce flood risk and are best suited to larger sites where they can be incorporated into landscaping schemes. ponds and wetlands also help with grit removal. algae and plants in wetlands can significantly assist with filtering and nutrient removal. |
| porous surface | a surface that infiltrates water to the sub-base across the entire surface of the material forming the surface, for example grass and gravel surfaces, porous concrete and porous asphalt. |
| portland cement | a type of cement made by burning limestone and clay; a basic ingredient in concrete. |
| post occupancy evaluation (poe) | a systematic way of comparing actual building performance with stated performance criteria usually undertaken by organisational or facility managers. a poe is usually undertaken after the building has been occupied for at least one year and seeks to measure and evaluate user satisfaction and whether the building suits its intended use, technical performance and value for money. |
| post-consumer recycled content (%) | composed of such material as paper or glass that has been recycled after being used, which means it is kept out of landfill. |
| potable water | water that is satisfactory for drinking, culinary and domestic purposes and that meets the requirements of relevant health authority legislation. |
| pozzolan | a type of silicon/alumina material that occurs naturally and is produced as a by product of coal combustion. when powdered and moistened it will react with calcium hydroxide and water; its most useable form is fly ash. |
| pre-consumer recycled content (%) | refers to leftover materials from the manufacturing process. using or selling this scrap doesn't divert material from the landfill; it is not truly recycled because it has never been used. |
| pulverised fuel ash (pfa) | a waste product of coal fired power stations consisting of tiny spherules of reactive silica, sometimes used as a component in mortars and grouts. |