Building envelope & environment

The building envelope is the archive's first and most passive preservation system. A well-designed envelope buffers external swings in temperature and humidity, so the mechanical plant works less and the collection experiences a gentler, more stable climate. Where the envelope is weak, the HVAC fights a losing battle and running costs soar.

International guidance - PD 5454, the ISO 11799 storage standard and the Bizot/IIC environmental principles - has shifted from tight setpoints toward stable, moderate conditions with controlled seasonal drift, because it is fluctuation, not a precise number, that drives most physical deterioration.

Thermal & moisture buffering

Mass and insulation slow the rate at which outside conditions reach the collection. A high-thermal-mass, well-insulated repository can hold conditions for days during a plant failure.

• Insulate to minimise heat gain; place the vapour barrier correctly for your climate to prevent interstitial condensation.
• Keep repositories internal - no external windows - to cut solar gain and UV.
• Design for stability: aim for gradual seasonal change rather than rigid year-round setpoints.

Target conditions & air quality

Set ranges appropriate to the dominant media, and control pollutants as well as climate.

• Mixed paper collections: broadly 16-19°C and 45-55% RH, with tight control of daily fluctuation.
• Cold storage for colour photography and film: lower temperatures in conditioned enclosures.
• Filter particulates (ISO 16890) and gaseous pollutants (SO₂, NOₓ, ozone); exclude light with UV-filtered, low-lux lighting on occupancy control.

Key takeaways

• A strong passive envelope reduces mechanical load, cost and risk during failures.
• Stability and controlled drift matter more than hitting a single exact setpoint.
• Manage light and airborne pollutants alongside temperature and humidity.