GRAVA GROUP

Complete renovation · Belgium

Transform your home, in the right order.

A high-performing renovation starts with a healthy building envelope and ends with everyday comfort. Explore the major technical choices, their dependencies and the next steps.

Plan your project Explore the systems

5key stages

C+ / D+controlled ventilation

1complete view

The Grava Group approachFrom diagnosis to finishing, one coherent renovation route.

Your renovation map

Understand the renovation before making choices.

The cards provide a quick overview of this page. Select a topic to jump straight to its full guide.

01 · Central ventilation

C⁺ and D⁺: two central systems, two different airflow strategies.

Do not choose by equipment alone. The right central system follows the floor plan, renovation depth, available routes for ducts, acoustic goals, energy ambition and the way the home will be used.

Central ventilation unit with planned ceiling duct routes — Air paths, technical space and service access must be planned before the finishes are closed.

Start with the airflow plan

Central ventilation is a coordinated installation, not a single appliance.

For both C+ and D+, define the rooms, air-transfer routes, wet-room extraction points, technical space, sound measures and maintenance access before finishing the ceilings and walls.

C+: natural supply with mechanical extraction
D+: mechanical supply and extraction, typically with heat recovery
Demand control can adapt flows to actual indoor-air needs
Final airflow rates and commissioning require a project-specific design

Plan your ventilation system Download the ventilation guide

Compare central systems

Select the principle before the installation is closed in.

C+ and D+ should be compared as complete indoor-air solutions. System type, ducts, terminals, access panels and controls are coordinated with insulation, windows, ceilings and interior layouts.

Renson Healthbox central C+ extraction unit

System C+

Natural supply. Mechanical extract.

Fresh air is admitted through purpose-designed supply inlets while a central unit extracts moist and polluted air from wet rooms. Demand control can adapt the extract rate to humidity, CO₂ or occupancy.

Central extract unit with extraction ducts
Defined air-transfer paths through the home
Compact approach when a full supply-duct network is not planned
Access is required for maintenance and commissioning

Discuss C+ for your renovation

Renson Flux central D+ balanced ventilation unit

System D+

Mechanical supply and extract, in balance.

A balanced system brings filtered fresh air into living and sleeping rooms and extracts used air from wet rooms. A heat exchanger can recover heat from the extracted air before it leaves the home.

Two mechanical airflows, designed and balanced together
Heat recovery helps limit ventilation heat losses
Requires duct routes, supply and extract terminals, and filter access
Best coordinated early with ceilings, joinery and service zones

Discuss D+ for your renovation

Overview of Renson central C+ and D+ ventilation systems

Illustrative Renson system overview. The final system, airflows and installation details must be selected for the specific home.

Practical guide · Grava Group

Read the ventilation guide.

Browse the guide in a wide horizontal viewer below, or download the PDF to review it with your project team.

Open the guide in Canva Download the ventilation PDF

RENSON VENTILATIE.pdf · author: Grava Group

02 · Window ventilation

Window vents are a separate part of the indoor-air strategy.

Window ventilation is not a C+ or D+ appliance. It is a dedicated way to provide background fresh-air entry at window level, which can be specified as an independent room-level measure or coordinated with a wider ventilation strategy.

Window vent integrated into a renovated window — The vent, frame, glazing and installation detail should be selected together.

Separate design decision

Design window ventilation around the window — not around a product label.

Frame profile, glazing build-up, acoustic requirement, desired airflow, façade exposure and airtightness detailing all determine the suitable vent. Its exact role in the home is confirmed in the project ventilation plan.

Can provide controlled background air entry at window level
Can be considered independently or alongside a wider indoor-air strategy
Must be sized and positioned before frame fabrication and installation
Does not automatically replace supply or extract components required by a designed central system

Explore Renson window vents Talk through window ventilation

Renson THM90Integrated background air vent

DucoFlat 80 SRVent profile for window frames

DucoLine 80 SRIntegrated frame ventilation profile

Renson Variavent FlatCompact glazing-related vent profile

03 · Thermal comfort

Choose the heating and cooling principle before selecting the equipment.

A boiler, air-to-water heat pump and air-conditioning multisplit are different approaches. Use the selector to compare their role in the home, the infrastructure they need and the questions to resolve before installation.

01 · Dual-purpose boiler 02 · Air-to-water heat pump 03 · Air-conditioning multisplit

Example Vaillant ecoTEC plus boiler technical-room installation

01 · Dual-purpose boiler

Gas boiler for space heating and domestic hot water.

A condensing dual-purpose boiler, such as a Vaillant ecoTEC plus, can provide central heating and domestic hot water from one appliance. It is assessed with the existing or planned radiators, underfloor heating, flue route, gas connection and hot-water demand.

Pairs with radiators and/or underfloor heating distribution
Requires correct flue, condensate and safety arrangements
Hot-water comfort depends on demand, pipe runs and simultaneous use
Must be sized and installed to the specific property and applicable requirements

Discuss a boiler solution

Air-to-water heat-pump system with buffer tank, domestic hot water and underfloor heating

02 · Air-to-water heat pump

Heat pump for water-based heating and hot water.

An air-to-water heat pump, such as Cube HP, Daikin or Vaillant solutions, transfers heat to a water-based heating circuit and can be coordinated with a cylinder, buffer tank, radiators or underfloor heating. Its suitability depends on heat loss, emitter temperatures, outdoor location and technical space.

Works with a water-based heating distribution system
Often coordinated with low-temperature radiators or underfloor heating
Outdoor unit position, acoustic treatment and drainage need early planning
Requires project-specific sizing, hydraulic design and commissioning

Download the Cube HP PDF Discuss a heat pump

Midea Breezeless E multisplit air-conditioning system with indoor units and outdoor unit

03 · Air-conditioning multisplit

Targeted cooling and heating through indoor units.

A multisplit air-conditioning system, such as the Midea Free-Match R32 example, connects one outdoor unit to several indoor units. It can provide room-by-room cooling and heating, subject to a design that considers capacity, line lengths, condensate drainage, electrical supply and outdoor-unit placement.

Multiple indoor units can serve selected rooms from one outdoor unit
Useful where room-by-room temperature control is important
Indoor-unit locations, refrigerant lines and condensate routes must be planned
Capacity and heating performance must be confirmed for the project conditions

Visit Midea heating & cooling Download the Midea PDF

Technical room: pipework, safety components and maintenance access must remain accessible.

After choosing the principle

Technical room, distribution and access must work together.

After selecting the main heating or cooling principle, the technical layout needs to accommodate pipework or refrigerant lines, safety components, controls, domestic hot-water equipment where required, noise measures and safe maintenance access.

Allow space for distribution, controls and safety components
Coordinate the technical room with floor, wall and ceiling finishes
Plan drainage, electrical supply and service access early
Keep the installation accessible for commissioning and future maintenance

Request a technical review

03 · Envelope and daylight

Modern entrance door and tall window in a renovated home — Installation quality protects the performance of the window and door system.

Grava Group

Windows and doors: comfort, quiet and fresh air.

New frames can reduce heat loss, draughts and external noise. Airtight installation is as important as the glazing. Plan the air inlets to match the selected ventilation strategy.

Glazing and frame profiles suited to the renovation
Airtight installation and carefully detailed connections
Vents compatible with C⁺ ventilation
Doors, thresholds and details that limit thermal bridges

Explore windows and doors View Renson window vents

04 · External insulation

A renovated facade combines envelope performance and architectural identity.

Grava Group

Facade: insulate, protect and create character.

External insulation with EPS or mineral wool helps reduce heat loss, address thermal bridges and renew the appearance of the home. The system must be complete: substrate, insulation, fixings, reinforcement, plinth and finish.

Check the substrate and moisture before work starts
EPS or mineral wool to suit the design
Continuous details around windows and at the plinth
A finish suited to the facade style and exposure

View facade works

05 · Protection from above

Renovated pitched roof with roof windows — A complete roof combines weather protection, insulation and a durable finish.

Grava Group

Roof and attic: secure, insulate, ventilate.

The roof protects the entire home. Check the structure, waterproofing, rainwater drainage and junctions before adding insulation. Insulation can be placed internally, externally or as a combination of both.

Diagnosis of structure and waterproofing
Internal, external or combined insulation
Appropriate underlay, vapour control and ventilation
Roof covering, gutters and junctions detailed with care

View roof works

The other renovation essentials

The works that make the home genuinely durable.

06 / WATER

Water supply and drainage

In a full renovation, replacing ageing pipes avoids reopening new floors and finished walls later.

07 / SAFETY

Electrical installation

Wiring, earthing, distribution board, RCDs and circuits need to meet current requirements and be inspected.

08 / HEALTHY

Moisture and plasterwork

Treat the cause — leak, rising damp, thermal bridge or insufficient air — before renewing the finishes.

09 / DRY

Foundation, basement and drainage

Managing water around the home protects foundations, basements and the new interior finishes.

10 / INTERIOR

Floors

Tiles, parquet, laminate, poured flooring or timber: choose after the substrate and building systems are prepared.

11 / FINISH

Walls and ceilings

Paint, plaster, gypsum board or decorative panels: choose according to flatness, acoustics and use.

Explore the renovation model in 3D.

Rotate, zoom and inspect the model directly in the viewer. It is provided as an interactive visual reference for the renovation journey.

Your project deserves a complete view

Let’s build a coherent renovation plan.

Let’s discuss your home, the right sequence of work and the technical choices that create comfort today and value tomorrow.

Contact Grava Group

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Easy Steps

Latest news

August 29, 2025
Renovation in Flanders 2026: Complete Guide to Subsidy Changes
Renovation in Flanders 2026: Complete Guide to Subsidy Changes
Reed More
August 29, 2025
Roof Cleaning
The company is proud to announce the completion of construction of a new residential complex in the heart of the city
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August 16, 2025
Facade Crepie renovatie
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August 29, 2025
Complex renovation
The company is proud to announce the completion of construction of a new residential complex in the heart of the city
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February 16, 2026
Roof renovation
Grava Group is proud to present another renovated home: Andenne Roof Renovation – 230 m² Natural Slate with 12 cm PIR Insulation and VELUX Replacement in Just 2 Weeks
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August 29, 2025
New roof – 20 houses
The company is proud to announce the completion of construction of a new residential complex
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August 29, 2025
Facade isolation Lier
The company is proud to announce the completion of isolation 1300 m2 in Lier
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August 29, 2025
Window installation
The company is proud to announce the completion of window installation for the nice house
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Projects

All projects

Neerpelt – Facade Renovation and Window Replacement in Neerpelt – Unique Combination of Render, Wood and Brick Slips for Maximum Design and Comfort
Location: Neerpelt
Full replacement of the facade, roof and windows in Ghent
Location: Ghent
Hasselt Facade Renovation – 540 m² Unique Combination of Brick Slips and White Render with 12 cm Insulation for Modern Appearance
Location: Hasselt
Date of construction: 09/2024
Buggenhout – Complete Facade Works, Insulation, Windows
Location: Buggenhout
Mechelen Large-Scale Project – 2430 m² Facade Insulation with Brick Slips and 214 New Windows for Maximum Energy Efficiency
Location: Mechelen
Renovation Tielt-Winge Apartment Building – 2350 m² Brick Slip Facade with PIR Insulation and Aluminum Windows for Maximum Energy Efficiency
Location: Tielt-Winge
Wachtebeke Megaproject – 3630 m² Facade Insulation with Brick Slips and 294 New Windows for Maximum Energy Efficiency
Location: Wachtebeke
Renovation Machelen – Pitched Roof with VELUX, Brick Slip Facade and Aluminum Windows for Maximum Comfort and Energy Efficiency
Location: Machelen
Renovation Lier – Brick Slip Facade, Flat Roof, Windows and PIR Insulation for an Energy-Efficient and Comfortable Home
Location: Lier
Date of construction: 08/2023
Roof Renovation 260m², Wood Facade and Window Replacement in Bruges – From Heat Loss to Energy Efficient and Modern
Location: Brugge
Lier Facade Renovation
Location: Lier
Andenne Roof Renovation
Location: Andenne
Diest – Large Facade Project
Location: Diest
Oud-Heverlee – Roof & Facade Renovation
Location: Oud-Heverlee
Niel – Roof Renovation & Skylight
Location: Niel
Rotselaar – Total Solar Project
Location: Rotselaar
Herenthout – Roof, Solar & Facade
Location: Herenthout
Kapellen – Modern Facade Renovation
Location: Kapellen
Mechelen – Crepi Facade Renovation
Location: Mechelen
Mechelen – Roof & Facade Renovation
Location: Kapellen
Stekene – Total Exterior Project
Location: Stekene
Essen – Modern Facade Renovation
Location: Essen
Pepingen – Roof & Facade Renovation
Location: Pepingen
Mortsel – Roof & Solar Panels
Location: Mortsel
Kessel-Lo – Apartment Building Project
Location: Kessel-Lo
Halle – Total Renovation: Roof, New Joinery & Light Clinker Facade
Location: Halle
Mechelen – New Roof & Facade Renovation
Location: Mechelen
Namur Complete Renovation
Location: Namur