Frequently Asked Questions

What is Passivhaus?

Passivhaus is a rigorous German standard for low energy homes. By insulating a building and making it almost completely airtight, it virtually eliminates heat loss and creates a building with very low impact on the environment. Any heating required comes from ‘passive’ sources such as sunlight, emitted heat from electrical appliances, heat from the ground, heat loss from the hot water tank, and even bodyheat meaning almost no extra heating energy input is required.

What is a Naked House?

A fully constructed, insulated and airtight house with windows and services (water, energy etc) installed that is awaiting fit out – kitchen, bathrooms etc.

Why is Airtightness so important?

Other than insulation, this is the single most important factor in achieving Passiv standard. Draughts are the enemy of home energy efficiency because of the amount of heat that is lost. So creating an airtight building ‘envelope’ by creating a continuous airtight layer throughout the house (for example installing triple glazed windows and doors) is essential. The airflow can then be actively managed via MVHR. An airtight building is also extremely efficient at keeping noise out.

What are Thermal Bridges?

A thermal bridge is where heat conducting materials draw heat out of a building either directly such as via a single uninsulated brick wall, or indirectly for example where a wooden joist touches an external wall through a cavity gap. Other examples include metal ties in cavity walls, and other outside connections to internal structures (for example certain types of balcony).

What is MVHR?

MVHR is Mechanical Ventilation Heat Recovery. In creating an airtight building ‘envelope’ to prevent heat escape, unless the airflow is actively managed, the interior of the building would become stagnant and humid (witness the common problem with condensation in properties with double glazing but no proper ventilation) An MVHR system delivers fresh air into a building in a controlled way, and uses the heat from the exiting stale air to heat the incoming fresh air. This not only provides ventilation and captures potentially wasted heat energy but also balances humidity levels and filters out dust particles. All this contributes to an environment of unequalled comfort levels with minimal energy usage. MVHR is most typically air-air, but can also be ground-air or earth-water.

What does it cost?

A Princedale Passivhaus is extremely cost efficient. Because so much more is done at the manufacture stage, it reduces site time and therefore cost. As a rough guide a Princedale Passivhaus starts at £1000m2 (including foundations, electrics plumbing and …)

How long does construction take?

Once foundations are laid construction to ‘naked’ state takes between1 – 3 weeks.

What are the running costs of a Passivhaus?

A Passivhaus uses very little energy, typically 8% of what a traditional house would use.

What are the benefits of Passivhaus?

There are multiple benefits, the chief amongst them being:
Low energy costs – protect yourself from the rapidly rising cost of energy
Low running costs – few moving parts mean much lower systems maintenance costs
Continuous comfort living environment – a perfectly balanced living environment; warmth, humidity, noise, dust are all managed for optimum levels.

What do you mean by continuous comfort living environment?

A living environment that is perfectly and constantly optimised for your comfort. Temperature is regulated to a constant, perfect level; humidity is managed for ideal comfort; noise levels are hugely reduced for a tranquil environment and dust particles are filtered out for fresh allergen free air.

What is CAD/CAM?

Computer Aided Design and Computer Aided Manufacture. Using state of the art software the house is designed in 3D down to the smallest detail, and then machine manufactured with absolute precision by computer driven technology.

How does Solar Thermal work?

Capturing heat energy from the sun
We use a drainback system

What is Photovoltaic (PV)?

Creating electricity from the sun

What is Triple Glazing?

Triple glazed windows have three layers of glass which not only provides extra heat insulation but also provides insulation from noise.

What does very low energy mean?

A low-energy house is any type of house that from design, technologies and building products uses less energy, from any source, than a traditional or average contemporary house typically in the range from 30 kWh/m²a to 20 kWh/m²a (9,500 Btu/ft²/yr to 6,300 Btu/ft²/yr).

Don’t timber frame buildings go rotten?

Actually no. Timber is actually a remarkably resilient and robust building material, and the UK has a history of Timberframe construction. Most Victorian terraces, for example, have timber frames. And there are plenty of Tudor and Medieval timberframe buildings still standing strong today.
Timber’s bad reputation arose in the late 1980’s and 90’s when insulation and doubleglazing were increasingly popular. These were used on new builds, but without proper ventilation and a lack of understanding about how certain materials trap moisture. This led to a build up of moisture in the timber which resulted in rotten frames – and again because of the lack of understanding, the frames themselves were blamed for the issue, not the ventilation and configuration.
This is why all our constructions come with ventilations systems built in to prevent this happening and a breathable system built into the timber frame through the use of breathable materials on the outer side of the frames..

What is EnerPHiT?

This is a low energy standard that has been developed in the UK specifically for use with period property retrofits. Because Passivhaus standard is so high, it can be difficult and expensive to achieve it in an existing buildings so EnerPHit has slightly lower airtightness requirements meaning retrofit projects can attain certification.

What does PHPP stand for?

PHPP is the name for the PassivHaus Planning Package. This is a design to used to develop the most effective combinations of materials and systems in the house. It is very accurate and has been developed in Germany over many years. It takes into account heating from sunlight, people in the house, heat loss through all elements, impact of the ventilation system on energy, appliances in the house etc. If used properly it will achieve a design that is optimised with minimal overheating in the summer and low or zero input of heat in the winter

What is SAP

SAP is the Government’s standard assessment process designed to measure CO2 created by buildings and measure energy loss.

What is BREEAM

A BREEAM assessment uses recognised measures of performance, which are set against established benchmarks, to evaluate a building’s specification, design, construction and use. The measures used represent a broad range of categories and criteria from energy to ecology. They include aspects related to energy and water use, the internal environment (health and well-being), pollution, transport, materials, waste, ecology and management processes.