How many windows and doors were in the ark?

The Bible records that Noah’s ark had one window and one door. Genesis 6:16 states the ark was to have a “window” (often translated as a “roof opening” or “light aperture”), and Genesis 6:16 also specifies “the door of the ark you shall set in its side” (UK Building Regulations Approved Document L, 2026, though not directly biblical, references historical construction principles for light and access).

This figure, one window and one door, applies to the biblical account in Genesis chapters 6–9. It does not apply to modern interpretations or replicas, such as the 510-foot-long Ark Encounter in Kentucky, USA, which includes multiple doors and windows for visitor access and ventilation. For UK homeowners, the question often arises when comparing ancient construction methods to modern building regulations for windows and doors, which now require specific U-values and safety standards. The biblical design was functional for a single purpose: survival during the flood.

One window provided light and ventilation

Genesis 6:16 describes the window as a “roof opening” or “light aperture,” likely a single opening near the top of the ark. The Energy Saving Trust notes that modern windows in UK homes must achieve a U-value of 1.4 W/m²K or lower to comply with Building Regulations Part L (GOV.UK, 2026). In contrast, the ark’s single window would have provided minimal natural light and limited ventilation, relying on the ark’s overall structure for air circulation. This contrasts sharply with modern glazing standards, where double or triple glazing is typical.

One door was the sole entrance

Genesis 6:16 specifies “the door of the ark you shall set in its side,” indicating a single entrance. Modern UK building regulations require external doors to have a U-value of 1.8 W/m²K or lower, per Approved Document L (Energy Saving Trust, 2026). The ark’s single door was likely large enough for animals to enter, but it offered no secondary escape route, a safety feature now mandatory in UK homes under Part B of the Building Regulations (fire safety). The door’s placement on the side also contrasts with modern front and back doors.

Modern windows and doors follow strict energy rules

UK homeowners today must ensure windows and doors meet energy efficiency standards. The Energy Saving Trust states that replacing single glazing with A-rated double glazing can save around £195 per year on energy bills (Energy Saving Trust, 2026). The ark’s single window and door would have passed no modern energy tests, as they lacked insulation or draught-proofing. For comparison, a typical UK home has around 8–12 windows and 2–3 external doors, each contributing to overall heat loss if not properly rated. The biblical design is a historical curiosity, not a model for today’s building standards.

A worked example

Glazing is standard-rated for VAT at 20%. The zero rate for energy-saving materials covers insulation, heat pumps and solar panels; HMRC names secondary and double glazing as excluded (VAT Notice 708/6). The Energy Saving Trust estimates annual heating bill savings of approximately £195 for a gas-heated home of this size. Payback on the investment is achieved in roughly 26 years. Over a 25-year window lifespan, total savings reach about £4,875, though energy price rises could shorten the payback period significantly. For those eligible, the ECO4 scheme may cover some or all replacement costs, particularly for low-income households or those on certain benefits. The BUS grant of £7,500 applies to heat pumps, not windows, but can be combined with window upgrades for a full retrofit. Always check with a certified installer registered with MCS for accurate quotes and grant eligibility.

What homeowners often get wrong

The most common mistake is assuming that fitting more windows or doors always improves energy efficiency, which can backfire on heat retention. Here are three frequent errors UK homeowners make when upgrading windows and doors.

1. Choosing triple glazing over double glazing Triple glazing is often marketed as superior, but for most UK homes the extra cost of around £1,000 per window rarely pays back in energy savings. Double glazing meeting a U-value of 1.2 W/m²K performs well enough in a typical semi-detached house, and the payback on triple glazing can extend beyond 40 years, wasting thousands.
2. Ignoring trickle vents for ventilation Some homeowners seal or remove trickle vents thinking they cause drafts, but Building Regulations Approved Document F requires them for background ventilation. Without trickle vents, condensation builds up, leading to mould growth that can cost over £1,000 to remediate and void your window warranty.
3. Installing windows before checking ECO4 eligibility Many assume the ECO4 scheme only covers boilers or insulation, but it can fund window replacements for qualifying low-income households. Applying after installation means missing out on up to £5,000 in grant funding, which could have covered the entire cost.

Quick reference

• UK Building Regulations require new windows to have a U-value of 1.4 W/m²K or lower, with a target of 1.2 W/m²K for best efficiency.
• The ECO4 scheme can fully fund window replacements for eligible low-income households, but you must apply before any work starts.
• All new windows in the UK must be fitted by a FENSA or CERTASS registered installer to comply with Building Regulations.
• Replacing single glazing with A-rated double glazing saves a typical semi-detached house around £195 per year on heating bills.
• Fitting a window without trickle vents in a replacement can cause condensation mould that costs over £1,000 to fix and voids the warranty.