General

Buying an Eco-House? (PDF)

What to ask for if you are thinking about buying a eco/green/low energy building.

Housing Association Air Test Report (PDF)

Report on housing association existing stock, showing air tightness before and after installation of external insulation.

Design

Intake Location Calculation (XLSX)

(Version 0.3)

On many projects we need to decide how close we can locate an air intake to a polluting exhaust or boiler flue. This workbook is for calculating the minimum recommended distances between intake and exhaust openings and boiler flues using the equation provided in Annex A of BS EN 13779: "Ventilation for non-residential buildings - Performance requirements for ventilation and room-conditioning systems". Note that this calculation does not take into account directional louvres.

Guide: Air to Water Heat Pumps

This guidance gives a comprehensive overview of the considerations when designing and specifying an air-to-water or air-source heat pump system. Aimed at designers at the initial stages of design, it highlights both straightforward concepts and some more complex aspects that are often overlooked - even by experienced services engineers, yet have a substantial impact on energy performance. Most can be applied to any project irrespective of building energy standards. The paper was co-authored by WARM Director Sally with industry colleagues, Gwilym Still and Alan Clarke for The Passivhaus Trust.

Guide: MVHR for single dwellings

This guide from September 2018 —co‑authored by Sally Godber, Director at WARM for the Passivhaus Trust—sets out the key tasks needed to ensure that MVHR systems are properly specified, reviewed, and delivered. Because project roles vary widely between design teams, the document focuses on what needs to be done rather than who must do it, helping all parties understand their responsibilities and ensure reliable, high‑quality MVHR performance in Passivhaus buildings.

Guide: Steel In Passivhaus Construction

High‑performance Passivhaus steel frame buildings are emerging across the UK—but designers and contractors have had little tailored guidance to support them. This paper closes that gap, sharing lessons learned from the UK’s first steel frame Passivhaus projects and highlighting key risks, design considerations and best‑practice approaches.

WARM Director Mike Roe contributed to this article for the Passivhaus Trust. It offers clear, practical principles to help clients, designers and contractors deliver reliable, high‑performance steel buildings with confidence.

Guide: How to build a passivhaus

WARM director Sally authored the 'Use of PHPP and quality assurance' chapter for this Passivhaus Trust guide. The publication brings together essential dos and don’ts for delivering successful Passivhaus projects, showcases inspiring certified Passivhaus and EnerPHit examples, and offers links to deeper guidance to help build your knowledge and confidence.

PHPP

PHPP WARM Results Sheet (XLSM)

(Version 7.0.8)

A graphical results sheet that can be added to any v9 or v10 PHPP. Also includes a revision history, so you can record the impact of changes to the PHPP.

Note: the section where the U-value calculations can be displayed is not functioning. Otherwise, this version is functioning well.

Additional shading sheet (XLSX)

(Version 4.2.4)

An add-in sheet for PHPP 9 and 10, which allows you to easily model shading objects that are discontinuous and/or which have transparency. These include trees, tower blocks, brise-soleils, juliet balconies and plant-on glazing bars.

WARM U-Value Corrections Calculator (XLSX)

(Version 1.0.3)

Calculates corrections for:

insulation moisture uptake in inverted roofs
AAC conductivity when used below DPC. Also corrects for moisture uptake and for mortar fraction.
screws passing through the insulation layer
NB: only for screws. NOT suitable for other fixing types/brackets/penetrations. As of PHPP version 10, this calculation is now included as an auxiliary calculation in the PHPP U-values sheet.