| feasibility study | a study undertaken to establish if a particular course of action will be viable and successful |
| fenestration | architectural term for windows and their placement. |
| filter drain | a linear drain consisting of a trench filled with a permeable material, often with a perforated pipe in the base of the trench to assist drainage, to store and conduct water, but may also be designed to permit infiltration. |
| filter strip | strip or area of vegetation used for removing sediment, organic matter, and other pollutants from runoff and wastewater. |
| first flush | the initial run-off from a site or catchment following the start of a rainfall event. as runoff travels over a catchment it will pick up or dissolve pollutants and the first flush portion of the flow may be the most contaminated as a result. |
| fly ash | ash residue from high-temperature combustion processes; can be used for fill material, soil stabilisation and waste remediation. electric power plants using western coal produce a non-toxic fly ash which can substitute for a portion of portland cement in concrete, to produce a strong, durable concrete |
| fossil fuel | a naturally occurring fuel rich in carbon and hydrogen formed by the decomposition of prehistoric organisms. |
| fsc - forest stewardship council | a chain of custody certification showing that the timber has been sourced from sustainable forest stock. |
| fuel poverty | fuel poverty usually relates to a household that needs to spend more than 10% of its income on fuel for cooking and heating. |