Many articles have been written about the new primary energy method and the certification classes. In our mind, however, PHPP 9 has more important new features: we explain what they are.
PHPP is the heat balance software to design passive buildings, developed by the Passivhaus Institut on the basis of ISO 13790, as well as the monitoring of several passive buildings from around the world.
With version 9, the developers worked a lot to improve and expand the software as a design tool. Unfortunately, the one feature that received the most attention is – in our mind – the least interesting one. That is, the new passive house classes.
NEW STRUCTURE OF PHPP 9
In the first place, the PHPP 9 has been reorganized, to better follow the usual workflow of data input; many of its worksheets have been merged.
The results of the calculation are now also stated at the top of each sheet, so that you can keep an eye on them while working on the specific values of the sheet.
Across the entire PHPP, a new error/warning detection system has been implemented, to make it easier to identify and correct them. The messages are highlighted in red (error) or blue (warning) in each sheet, next to the values that are incorrect or inconsistent.
All these messages are also repeated in the new Check sheet, which is extremely helpful as an overview of the whole PHPP.
The new Variants sheet was developed to evaluate step-by-step energy retrofits, however this new feature is a great design tool for new constructions as well.
A Variant is a scenario of how the building can be constructed: within each variant, several different items can be treated as a variable, such as the type and thickness of the insulation, the type of windows, the HRV unit and so on.
As an example, the Variants for a new construction could look like:
Variant #1: insulation EPS with graphite 240 mm; windows type “X”; HRV with 75% recovery;
Variant #2: insulation EPS with graphite 200 mm; windows type “Y”; HRV with 80% recovery;
Variant #3: insulation rock wool 240 mm; windows type “Z”; HRV with 93% recovery.
For a step-by-step retrofit, it could look like this:
Variant #1: existing conditions;
Variant #2: insulation of external walls;
Variant #3: insulation of walls; new windows + ventilation;
Variant #4: insulation of walls; new windows + ventilation; roof insulation.
Basically, any input cell in PHPP (yellow cells) can be turned into a variable of a Variant.
When the Variants are defined, the software runs a PHPP calculation for each scenario. The results of the Variants are shown next to each other in the Variants sheet.
Once the Variants have been defined, you can switch to the Comparison worksheet, to compare two scenarios from an economic point of view. In this sheet, you enter further data such as construction costs, as well as the gross cost of energy and maintainance and the interest rate. You also enter the present value of incentives or tax breaks, if they are available.
You can customize the expected life cycle of the single components (opaque envelope, windows, ventilation etc.): based on this, PHPP calculates the economic conveniency of the investment for the more performing Variant. It is not possible to customize an estimated increase of the energy cost, as this is supposed to remain constant over the calculation period.
Far too often, the economic feasibility of a project is only based on the initial cost of construction alone, regardless of the operational and maintenance costs. With PHPP 9, you can easily calculate future energy bills, so that the overall economic picture of the building can be thorough. The economic calculation include the costs for heating, cooling and ventilating the building, as well as the auxiliary energy related to those systems. The cost of energy employed for domestic hot water and lighting, as well as other domestic uses, are not included.
In the PHPP section dedicated to the thermal envelope, you can see how some older sheets have been merged together.
The result is the new Components sheet: here you can either customize envelope components such as glass, window frame, HRV/ERV units, or you can select certified ones from the database of the Passivhaus Institut. If you want to use certified assemblies for the opaque envelope (as opposed to creating custom ones in the U-Values sheet), in the Components sheet you can find the list of the certified construction system (including the PSI values of their certified junctions).
As far as the data input for shading, the workflow has been simplified substantially with the release of DesignPH, the SketchUp plug-in that allows to model passive buildings in 3D. Unfortunately, it is not yet possible to run a shading calculation as accurate as you can do in EcoDesigner. We hope that DesignPH is going to be developed in order to do so in one of the next versions of the software.
PRIMARY ENERGY RENEWABLE
We finally come to the news about primary energy. Up to the previous version of PHPP (v 8.5), the limit of primary energy for a passive building was set at 120 kWh/m2y, regardless of renewable energy systems provided with the project.
With the new version of PHPP, the whole concept of primary energy has been reviewed. The calculation is now based on a future scenario where all energy is going to come from renewable sources. In such a scenario, both demand and supply are going to be variable on a seasonal basis. Seasonal energy storage is going to be necessary (probably via the renewable production of methane).
The longer the energy needs to remain stored, the less efficient the system is going to be. This is the case of winter heating, that requires more energy than what can be produced in the same period of time with renewable sources.
This is the reason why the conversion factors to calculate the primary energy renewable (PER) are split among the different uses (heating, cooling, domestic hot water and so on), and they are climate dependent.
The result of the primary energy calculation is not a single number, but two: demand and supply.
For each building, you can calculate demand and supply of primary energy renewable, based on the scenario described above, where all energy is going to come from renewable sources.
The combination of the two values, demand and supply, determines what kind of “class” of passive house your building falls under.
PHPP 9 and DesignPH are available in English.