Utilising PHPP as a tool to design low-energy homes
In the quest for more sustainable and energy-efficient homes, many Self Build enthusiasts are turning to innovative design methodologies. One such powerful tool gaining popularity in the Self Build community, which strives to build eco homes, is the Passive House Planning Package (PHPP). This software is a tool that allows us to test the design against the performance criteria.
The tool is not only for those striving to build a certified Passive House but can be successfully used to assess the design heating demand/load figures, help in the choice of materials and establish construction methods for those who wish to build a low-energy home. It is a powerful tool that will allow you to make informed choices for your build with a budget in mind.
If you want to build an eco home, you are at the right place. In this article, we explore the key concept of the Passive House principles and how using the PHPP software can add value to your Self Build project to create an eco-friendly home.
UNDERSTANDING PASSIVE HOUSE PRINCIPLES
The principle of low-energy design, including the Passive House standard, is based on the Fabric First approach, and the key to ensuring the transition to low-carbon heating is adopting this approach.
At its core, the Passive House standard is a building performance criterion that focuses on achieving exceptional energy efficiency, indoor comfort, and superior air quality. The main aspects of the Fabric First approach and Passive House design include excellent insulation, airtightness, thermal bridge-free construction, high-quality windows, and controlled mechanical ventilation.
The Passive House standard’s strengths lie in its simplicity. Using Fabric First with these simple key elements along with PHPP software will allow you to achieve a low-energy home.
Utilising PHPP allows us to assess and optimise these factors to create a sustainable dwelling. This tool advises our clients on where their investment is most valuable in the construction process. Leveraging PHPP during the initial design stages proves especially advantageous, as it not only informs the design direction but also steers us toward an optimal building configuration, thereby maximising energy efficiencies and delivering the best product for self-builders.
WHAT IS PHPP SOFTWARE?
PHPP is a specialised software tool based on an Excel spreadsheet developed by the Passivhaus Institute in Germany. It serves as the energy modelling and design verification tool for Passive House projects. The software takes into account various factors like house location, orientation, house level in terms of how high the building is sitting above sea level, building geometry – form factor, building fabric, ventilation strategy, solar gains and internal heat sources to calculate the energy performance of the building throughout the year.
The software needs to be used by a certified Passive House Designer or Consultant because it is quite complex, and there is very little room for error when it comes to achieving the Passive House criteria. But at the same token, the software can be used on those projects that are not necessarily striving to achieve the certification. It allows testing the design and brings all the benefits in terms of the design assessment against the thermal performance criteria helping in making the design decisions, as well as assisting the self-builders in specification decisions. It allows to maximise the potential of the site location and orientation within the new home and draws on all those passive and available elements from the surrounding environment to be incorporated into the design.
In consideration of your Self Build budget, at ACA, we can offer varied levels of the PHPP service, which are specifically catered to your project requirements, including a reduced preliminary service to guide the design and specification from the initial stages.
It is advised to utilise PHPP to test the initial design, which would eliminate the need for potential future modifications, should the results prove not satisfactory to meet the set energy performance criteria.
The preliminary PHPP calculations should ideally be carried out before applying for planning submission to allow for incorporating any changes to the design before the approval is granted. This negates the need of having to go through the planning process twice, which would impact the project timescales, and will cost more. For example, if there is an issue with overheating, consideration could be given to the size of the windows or to the specification of external shading devices. In planning terms, these changes, however, could constitute a material change, at which point you may be required to re-apply for approval.
THE PHPP SOFTWARE CAN BE USED RETROSPECTIVELY
If you already have planning permission, at ACA we can test the completed design within the PHPP software to see what performance criteria are achievable. The software will provide the self-builder with the following output:
- Heating demand/load figures
- Cooling & dehumidification demand
- Frequency of Overheating
- Frequency of excessive-high humidity
- Primary Energy Demand (non–renewable and renewable)
At this stage and before the technical drawings and specification are progressed, the software helps in decision-making in regard to the build specification, for example, to estimate the level of insulation needed, and advice can be provided on the construction system to use. At that point, you will then be able to obtain quotes for the heating system, windows, doors etc.
WHY WOULD YOU NEED PHPP IF YOU ARE DOING A SAP CALCULATION?
SAP and PHPP serve distinct purposes: SAP supports building warrant applications by demonstrating compliance with government energy standards. It generates an EPC certificate for property sale/rent. PHPP assesses overall building performance and energy rating, focusing on in-use performance, internal comfort, and specific local climate data.
SAP is mandatory for building warrants, concentrating on external fabric and workmanship, while PHPP emphasises internal comfort and accurate energy use assessment. PHPP employs local climate data for precise energy use assessment, particularly heating demand, aiding project budgeting. SAP uses UK average data for consistent EPC comparison.
PHPP is more accurate for energy efficiency improvements and cost-effective house operation.
HOW TO UTILISE THE PHPP SOFTWARE IN THE DESIGN PROCESS
First, you can opt to carry out preliminary PHPP calculations at the initial design stage. This will guide the design of the building in terms of the house location and orientation within the site, the form of the building, the sizes and location of the windows etc.
At this point, we test any impact on planning, but also, these early calculations provide the above-mentioned figures of heating demand and load that will allow the self-builder to start making enquiries with heating and ventilation suppliers and inform the project budgeting.
All external components of the building can be therefore assessed to guide the design at the initial stages and the planning stages to create a design that is energy efficient. As we said before, this way, you won’t have to go back to planning with revised designs after you gained planning approval.
After the preliminary PHPP calculation, you’re going to have quite a lot of information that you can use and start engaging with potential building services suppliers for quotes and investigating the building materials, which will allow you to make informed decisions regarding the design detailed specification required for next stages of the design process.
Preliminary PHPP calculation makes the whole Self Build process much easier from the onset and allows you to move on to the next stages, having all the crucial information of your project and planning accordingly.
When progressing to the next stage, typically involving architectural services in a technical capacity, and generating drawings for building regulation compliance, it becomes essential to define your chosen construction method. Providing your architect with comprehensive information and specifications is pivotal. The information you will get from the PHPP exercise will enable them to assemble the requisite packages for building control approvals quicker and help you make decisions and accelerate the process.
At ACA, we are often asked to provide this Passive House consultancy service in parallel with your Architect, which along with low energy guidance on specification and detailing proves popular amongst our clients.
If you already have an existing design with planning approval, there’s nothing to stop you from undertaking PHPP analysis at that point. Let’s say you’ve got a design ready and planning permission secured. At this point, you could reach out to a Passive House Designer to run initial modelling using PHPP software. This will help you to figure out where you could make smarter investments, like adding more insulation to roofs and walls or if investing in higher window specification brings more benefit in terms of heat loss. As there is a point after which upgrading the building elements will not provide much of the benefit in terms of the overall house energy performance, without using the PHPP tool, this is difficult to judge and estimate.
These decisions guide your architect’s direction. You have, therefore two options here: you can use this service along with ACA full architectural service or combine it with your current architect. Alternatively, if your architect’s role is completed and fees paid, you could consider involving a specialist in low-energy home design to progress further project works stages. The goal is to ensure your home is as energy efficient as possible and the team appointed for your project specialises in the design and detailing of low-energy homes with particular emphasis on airtight and cold bridge-free construction methods or eliminating those issues from your build.
HIGH-LEVEL OUTPUT FROM THE PHPP CALCULATION
- Energy Balance: PHPP calculates the overall energy balance of the building, taking into account both heat losses and heat gains. This analysis helps identify areas where energy efficiency can be improved, leading to reduced energy demands.
- Optimal Insulation: By using PHPP, self-builders can determine the most appropriate insulation thicknesses for floors, walls and roofs based on climate data and desired comfort levels. Adequate insulation levels ensure minimal heat loss and consistent indoor temperatures.
- Airtightness: PHPP helps evaluate the airtightness of the building envelope and its varied designed levels on overall energy performance. In basic terms, reducing air leakage enhances energy efficiency and prevents drafts and moisture-related issues, and the onerous value set by Passive House Institute at 0.6 air change rate @50 Pa pressure difference is a very good level of performance criteria for a self-builder to aim for.
- Window Selection: PHPP allows for the optimization of window placement, orientation, and glazing type. This ensures maximum solar gain during the colder months and minimizes overheating in summer.
- Ventilation Strategies: The software helps in establishing the ventilation strategy and specification of an efficient mechanical ventilation system with heat recovery, ensuring a constant supply of fresh air without unnecessary heat loss.
BENEFITS OF UTILISING PHPP IN SELF-BUILD PROJECTS
A lot of people come to us and say, “What, if I just throw all of this insulation in the building, why do I need to do calculations?” Well, the bottom line is that you could be throwing up quite a lot of that insulation without knowing what benefit that actually gives you. In some cases, it could be very little once offset against the additional costs of materials. Therefore, although the PHPP service is an add-on to the standard architectural service, in the longer term, it can save you a considerable amount of money.
The calculation is almost like going back to basics and working with actual figures because otherwise, it’s just arbitrary speculation on the building’s thermal performance. The bottom line is that you could be spending more money than you need to in terms of meeting all your performance criteria.
At ACA, one of our main questions from the start of the design process is ‘What energy performance goals do you have?’ and then we guide you to different options depending on your budget. You could be aiming for fabric first approach or low-energy building or a Passive House standard, which is the most stringent out of the three mentioned. For any of these energy levels, we strongly advise a PHPP calculation. Don’t rely on guesswork; get accurate insights for better results.
At ACA, we take pride in providing cutting-edge services that empower self-builders to realise their low-energy home dreams. Through our expertise in utilising the Passive House Planning Package (PHPP), we guide clients from the early stages of design to achieving optimal energy performance, as well as providing professionals like architects and structural engineers already appointed with guidance on the construction of low-energy homes.
By combining PHPP calculations with our architectural services, we help clients make informed decisions, streamline the Self Build process by providing a comprehensive service, and create sustainable homes that stand as a testament to energy-efficient living.