1. Why the early phase decides
The position in professional sources is unambiguous here, and it is the basis of the whole article. Energy performance is decided in the early phase.
Energy performance must be taken into account in the early planning phase, because choices made at a later stage are generally not sufficient to offset energy-inefficient choices made early. The choice of a ventilation unit is cited as an example, being a typical late decision.
The reason is simple, and it is worth putting to the client in these terms: early decisions determine the energy demand, later decisions only the efficiency with which it is met. A small demand is easy to cover, and a large demand cannot be made small by an efficient device.
2. What a late choice of equipment does not repair
Four things are already settled in the early phase, and no device makes up for them. They concern the massing and the orientation.
| What is settled | Note |
|---|---|
| The building's shape and its area-to-volume ratio | determines the surface through which heat is lost |
| Orientation and the placement of glazed areas | determines solar gain and load |
| Roof orientation and shading | in Estonia may determine which requirement applies |
| The basic solution of the external envelope | determines the size of the demand |
The third row is particular to the Estonian context, because it affects not only the solution but which requirement applies at all. That is why the roof belongs with the architectural decisions rather than in the building services chapter.
3. In what order to take decisions
Four steps whose order affects the outcome more than any individual choice. The order cannot be restored later.
| # | Decision | What it determines |
|---|---|---|
| 1 | Shape, orientation and volume | the basis of the energy demand |
| 2 | External envelope solution | the size of the demand |
| 3 | Building services | the efficiency with which the demand is met |
| 4 | Renewable energy solution | covers the remainder |
The fourth step cannot be used to compensate for the first, as covered by the article on the nearly zero-energy requirement. The requirement is two-level precisely to exclude that compensation.
4. What the calculation gives you
According to professional sources the calculation is not merely evidence of compliance, and this is the practical turn of the article. It is also a design tool.
An accurate calculation model makes it possible to run through different scenarios during design, for example insulation thickness against the efficiency of the heat source. The aim is to find the most economically viable solution, not merely one that meets the requirements.
The timing of the commission follows from this: the calculation is worth ordering earlier than at the last moment, because it then also serves the design. A calculation ordered late evidences compliance or its absence but no longer influences the solution.
5. Why it costs more later
Three consequences of late attention, and they escalate. They run from redesign to added plant.
Where the calculation shows non-compliance at a late stage, the solution has to change. A change at a late stage usually concerns building services, which is a more expensive route to the same result, and in the worst case the external envelope solution has to change, which affects the entire project.
This is the same pattern that holds throughout construction: early decisions are cheap, late ones expensive. With energy performance the pattern is only sharper, because an error in the first step cannot be corrected in the fourth.
Summary and four practical rules
Energy performance follows from early decisions: shape, orientation, roof orientation and the envelope solution determine the energy demand, and later choices determine only the efficiency with which it is met. The order of decisions has four steps, and the fourth, renewable energy, cannot be used to compensate for the first, since the requirement is two-level precisely to exclude that. A calculation is not merely evidence of compliance but a means of comparing scenarios, provided it is commissioned early enough.
Four rules: bring the energy question into the first design phase. Assess roof orientation and shading as an architectural decision. Commission the calculation while it can still influence the solution. Explain to the client that a late change concerns building services and is a more expensive route to the same result.
This article offers professional orientation as at the date of verification. It replaces neither the regulations in force nor the assessment of a competent specialist.