Heating replacement in Aargau and Zurich: assess the building before choosing the system

Start with existing conditions, not the appliance

Before selecting a system, document current operation: building year and heated area, energy source, several years’ consumption, hot water, heating curve and problem rooms. Include known roof, façade, window or basement-ceiling upgrades. This does not replace heat-load calculations but identifies what specialist design must answer.

Old heating may be oversized or use higher temperatures than the building needs after later upgrades. The old boiler rating is therefore not a reliable ordering value. Derive capacity from current condition and actual use, including planned insulation or windows that may change future demand.

Check distribution and required temperatures

Radiators or underfloor heating alone do not establish the flow temperature needed on cold days. Assess emitters, hydraulics, room temperatures and settings together. Underserved rooms may indicate small emitters, air in the system, poor settings or envelope defects.

For comparison, establish whether distribution will remain, be hydraulically balanced or extended locally. Include pipes, pumps and storage. Quoting only the generator leaves a critical interface unresolved. Show assumed system temperature and required modifications in the quotation.

Filter options by site and building

Not every renewable system suits every site. District heating needs an available connection and suitable terms. Ground probes need site-specific assessment and procedure. Air-to-water heat pumps depend on siting, airflow, access, condensate and noise. Wood systems need suitable storage and delivery space. Check exclusions before detailed prices.

Then compare technical and economic options on the same basis: investment, associated work, expected operation, maintenance, life assumptions and future renewal. Brochure generalities are insufficient because systems, envelope and site set the conditions.

Coordinate siting, noise and electrics early

For outdoor heat pumps, distance, direction, façade reflections and surroundings affect acoustic assessment. Do not fix the position only after choosing equipment and delivery dates. Reserve maintenance and airflow space and safe condensate drainage. Coordinate penetrations with envelope, fire safety and interiors.

Include electrics in the early survey. The responsible electrician assesses service connection, distribution, major existing loads and planned capacity. Consider future solar, EV charging or energy management together. They need not all be built simultaneously; this avoids conflicting space and connection choices.

Check cantonal procedures separately

Aargau and Zurich have separate implementation and subsidy routes. Municipality, system and position also matter. A Swiss-wide checklist can structure, but not replace, assessment. Record procedure status, evidence and responsible body as their own planning item.

Zurich’s current information states that every heating replacement is an alteration requiring permission and that the WTA application goes to the municipal building office. Systems may need further evidence, such as noise or water protection. Renewable solutions have priority under the stated technical and economic conditions. Do not apply these Zurich rules unchecked to Aargau.

Aargau’s funding page refers to specific and general conditions and its application portal. Determine required documents from municipality, system and measure. Ask not only which heating fits, but which procedure must be completed or started before each project decision.

Clarify funding before orders and construction

Grants are not automatic retrospective invoice discounts. Aargau explicitly requires application before work begins. Check the chosen measure’s current conditions before binding orders or subsidy-relevant work starts.

For 2026, Zurich confirms support including replacement of fossil heating with certain heat pumps or district-heating connections. Still check exact eligibility and amounts for the project under the current programme. No universal amounts are given here because measure, capacity, building and timing affect eligibility.

GEAK or GEAK Plus can structure broader renovation decisions. GEAK assesses envelope, overall efficiency and direct CO₂ emissions; Plus adds modernisation options. Clarify for the canton and project whether a report is mandatory, subsidised or simply useful.

Compare quotations with the same scope

An appliance price is not a complete replacement quote. Allocate removal and disposal, generator, storage, hydraulics, electrics, controls, routes, core drilling, bases, noise protection, commissioning and documentation clearly. Scaffolding, excavation, reinstatement and temporary heat may also apply.

State unresolved conditions as assumptions, options or investigations rather than silently including them: electrical reserve, emitter suitability or routes, for example. Assign design, permissions and funding applications to a responsible party for each option.

From survey to controlled commissioning

After selection, complete detailed design and approvals: final equipment and tank positions, routes, electrics, penetrations and reinstatement. Programme delivery, shutdown, temporary provision and checks before returning the installation to occupants.

Commissioning is more than switching on. Adapt settings, curve, hot water, pumps and controls to the building and explain them clearly. Handover includes agreed tests and permission records, operating and maintenance information and funding documents. An early-operation follow-up may be useful because settings are judged under real conditions.